As the Paleozoic Era gave way to the Mesozoic, some 225 million years ago (MYA), an ovoid upwarping of Earth's crust developed in what is now northern Arizona. Reinforced during the Laramide Orogeny (the formation of the Rockies, 70 MYA), this broad ridge was eventually covered by layers of Mesozoic and Tertiary sediments (both erosional and volcanic). Late in the Tertiary Period, the Miocene-Pliocene Uplift (stretching from about 15-5 MYA) lifted the entire Colorado Plateau and its rim of mountain ranges another 5000 feet, increasing stream erosion across the Province. Rising on the west side of the Continental Divide, the Colorado River flowed westward and gradually southward to enter the Sea of Cortez; en route, it crossed northern Arizona, entrenched in the younger sediments that covered the Kaibab-Coconino ridge. As the Colorado Plateau rose beneath it, the river was forced to cut down through this ridge of Paleozoic rock (and the upper layer of the ancient Precambrian basement that lies beneath it). Augmented by the wet climate of the Pleistocene (2 to 0.01 MYA), the Colorado thereby sculpted the Grand Canyon, the most spectacular chasm on our planet.
The ridge itself, oriented NNW to SSE, has since been uncovered by erosion. Streams from its eastern edge drain directly into the Colorado (or into the Little Colorado south of the Grand Canyon), while its northwest flank drains to the Colorado via Kaibab Creek and its southwest flank feeds the Cataract River, another tributary of the Colorado. The exposed ridge is composed primarily of Kaibab limestone overlying Coconino sandstone; that portion north of the Grand Canyon is known as the Kaibab Plateau while its segment south of the Canyon is referred to as the Coconino Plateau. The rock strata of the plateau, deposited during the Permian Period, form the upper layers of the Grand Canyon
The Kaibab Plateau rises to elevations that exceed 9200 feet, supporting a rich forest of fir, spruce and aspen, giving way to ponderosa pine and then pinon-juniper woodlands at lower elevations. The Coconino Plateau is 7400 feet above sea level at the south rim of the Grand Canyon and gradually lowers toward the west, south and east; it is covered primarily by ponderosa pine parklands. South of the Coconino Plateau, the landscape is dominated by the high peaks and scattered cones of the San Francisco Volcanic Field, including Humphreys Peak (12,633 feet), the highest point in Arizona.
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Kamis, 12 Juli 2012
Jumat, 06 Juli 2012
Colorado's Black Canyon
Near the end of the Mesozoic Era, as the Cretaceous Sea retreated to the southeast, Colorado was a relatively flat landscape of wetlands, sandhills and primitive forest. Then, about 70 million years ago (MYA), pressure within the North American craton crumpled up the Rocky Mountains, pushing ancient Precambrian rock up through the overlying Paleozoic and Mesozoic sediments.
As soon as they formed, the forces of erosion began to act on these new mountains, filling the intervening valleys with debris. About 35 MYA, volcanism developed in central and southwestern Colorado, lifting the West Elk and San Juan Mountains; the copious ash, pumice and lava from these eruptions also coated the valleys and basins of that region. By 10 MYA, the Gunnison River had formed; rising on the west side of the Continental Divide, in the Sawatch Range, and receiving large tributaries from the West Elk Mountains, to its north, and the San Juans, to its south, this river flowed west to join the Colorado. Entrenched within the erosional and volcanic debris that had settled across the broad, intervening basin, the Gunnison was forced to cut into a ridge of Precambrian gneiss and schist, east of present day Montrose, that was buried within the sediments. Since that time, the river has sculpted the Black Canyon of the Gunnison from that ancient rock, a process that was augmented during the cooler, wetter climate of the Pleistocene.
Almost 50 miles in length, the Black Canyon is up to 2720 feet deep and 1100 feet across at its rim; at river level, it is much narrower, only 40 feet wide in one area. The Painted Wall, on the north flank of Black Canyon, is named for the light-colored lava rock that laces its surface and is the tallest cliff in Colorado, dropping 2250 feet. Within the canyon, the Gunnison River drops 43 feet per mile, a grade that is almost six times steeper than the Colorado River's course within the Grand Canyon. Named for its shaded walls, hidden from the sun by its deep and narrow topography, the Black Canyon of the Gunnison is protected within a National Park that stretches along its middle (and most spectacular) 14 miles. Farther west, the Gunnison is thought to have carved Unaweep Canyon through the Uncompahgre Plateau, later diverted northward by a landslide to join the Colorado west of Grand Junction (see my blog on 12-27-10).
As soon as they formed, the forces of erosion began to act on these new mountains, filling the intervening valleys with debris. About 35 MYA, volcanism developed in central and southwestern Colorado, lifting the West Elk and San Juan Mountains; the copious ash, pumice and lava from these eruptions also coated the valleys and basins of that region. By 10 MYA, the Gunnison River had formed; rising on the west side of the Continental Divide, in the Sawatch Range, and receiving large tributaries from the West Elk Mountains, to its north, and the San Juans, to its south, this river flowed west to join the Colorado. Entrenched within the erosional and volcanic debris that had settled across the broad, intervening basin, the Gunnison was forced to cut into a ridge of Precambrian gneiss and schist, east of present day Montrose, that was buried within the sediments. Since that time, the river has sculpted the Black Canyon of the Gunnison from that ancient rock, a process that was augmented during the cooler, wetter climate of the Pleistocene.
Almost 50 miles in length, the Black Canyon is up to 2720 feet deep and 1100 feet across at its rim; at river level, it is much narrower, only 40 feet wide in one area. The Painted Wall, on the north flank of Black Canyon, is named for the light-colored lava rock that laces its surface and is the tallest cliff in Colorado, dropping 2250 feet. Within the canyon, the Gunnison River drops 43 feet per mile, a grade that is almost six times steeper than the Colorado River's course within the Grand Canyon. Named for its shaded walls, hidden from the sun by its deep and narrow topography, the Black Canyon of the Gunnison is protected within a National Park that stretches along its middle (and most spectacular) 14 miles. Farther west, the Gunnison is thought to have carved Unaweep Canyon through the Uncompahgre Plateau, later diverted northward by a landslide to join the Colorado west of Grand Junction (see my blog on 12-27-10).
Jumat, 29 Juni 2012
Life in the Universe
Current scientific evidence indicates that the Universe is 13.7 billion years old and that the galaxies formed 12 billion years ago. Yet, our home star, the sun, is less than 5 billion years old, the Earth formed just 4.6 billion years ago, unicellular life did not evolve on our planet until 3.6 billion years ago and we humans did not appear until 130,000 years ago. Countless suns, their solar systems and the life that inhabited their planets likely evolved and disappeared long before our own sun and planet came into existence.
Among the 100 billion galaxies and trillions of stars that stretch across the ever-expanding Universe, there are surely millions of other planets that sustain life which, in many if not most cases, has progressed farther along the evolutionary tree than has life here on Earth. In other words, it is almost a certainty that many human-like civilizations inhabit this Universe, most of which are more advanced than our own.
It is understandable that religious persons might find these rational facts too threatening to contemplate but it is disconcerting to hear scientists and scientific journalists question whether life exists elsewhere in the Universe. Sitting here on our smallish planet that circles a modest-sized star on an outer band of a massive galaxy, it is absurd to suggest that we might be the only intelligent beings that inhabit the billions of galaxies. The Universe surely teems with life and it is only our irrational self-importance that keeps us from embracing that fact.
Among the 100 billion galaxies and trillions of stars that stretch across the ever-expanding Universe, there are surely millions of other planets that sustain life which, in many if not most cases, has progressed farther along the evolutionary tree than has life here on Earth. In other words, it is almost a certainty that many human-like civilizations inhabit this Universe, most of which are more advanced than our own.
It is understandable that religious persons might find these rational facts too threatening to contemplate but it is disconcerting to hear scientists and scientific journalists question whether life exists elsewhere in the Universe. Sitting here on our smallish planet that circles a modest-sized star on an outer band of a massive galaxy, it is absurd to suggest that we might be the only intelligent beings that inhabit the billions of galaxies. The Universe surely teems with life and it is only our irrational self-importance that keeps us from embracing that fact.
Sabtu, 23 Juni 2012
Avalonia
There are few terranes that illustrate the science of plate tectonics and continental drift better than Avalonia. This micro-continent formed as a volcanic island arc along a subduction zone off the African Coast; at that time, late in the Precambrian Era, Africa was attached to the other southern continents to form Gondwana, which stretched across the South Pole. During the Cambrian Period, some 530 million years ago (MYA), as shelled marine life was exploding in diversity, Avalonia rifted from the African Plate and drifted northward ahead of the Rheic Ocean, which opened between it and Gondwana.
Late in the Ordovician Period, some 450 MYA, Avalonia docked with Baltica, the craton that now underlies Scandinavia, Eastern Europe and western Russia. This combined continental mass then collided with Laurentia (proto-North America) during the Silurian Period (440 MYA) as plants and animals were first colonizing the land; the collision forced up the Northern Appalachians, an event known as the Acadian Orogeny. When the Earth's land masses merged into Pangea during the Permian Period, about 270 MYA, Avalonia was caught in the middle, compressed between the northern and southern continents.
As the Tethys Sea opened east to west, some 200 MYA, Avalonia remained with Laurasia (the combined northern continents). During the Jurassic (150 MYA), the Atlantic Ocean began to open, splitting Avalonia as it divided the North American and Eurasian Plates. Today, fragments of Avalonia form coastal New England, Nova Scotia and the Avalon Peninsula of Newfoundland on the North American Continent; across the Atlantic, it is represented by Wales, England and the northern portion of Western Europe. Small fragments of Avalonia have also been identified in South Carolina and along the western rim of the Iberian Peninsula.
Late in the Ordovician Period, some 450 MYA, Avalonia docked with Baltica, the craton that now underlies Scandinavia, Eastern Europe and western Russia. This combined continental mass then collided with Laurentia (proto-North America) during the Silurian Period (440 MYA) as plants and animals were first colonizing the land; the collision forced up the Northern Appalachians, an event known as the Acadian Orogeny. When the Earth's land masses merged into Pangea during the Permian Period, about 270 MYA, Avalonia was caught in the middle, compressed between the northern and southern continents.
As the Tethys Sea opened east to west, some 200 MYA, Avalonia remained with Laurasia (the combined northern continents). During the Jurassic (150 MYA), the Atlantic Ocean began to open, splitting Avalonia as it divided the North American and Eurasian Plates. Today, fragments of Avalonia form coastal New England, Nova Scotia and the Avalon Peninsula of Newfoundland on the North American Continent; across the Atlantic, it is represented by Wales, England and the northern portion of Western Europe. Small fragments of Avalonia have also been identified in South Carolina and along the western rim of the Iberian Peninsula.
Jumat, 22 Juni 2012
Australia's Great Basin
The Lake Eyre Basin of east-central Australia is a vast topographic bowl within which streams drain toward the lowest part of the basin, never reaching the sea. Covering 440,000 square miles from southwestern Queensland to South Australia and from the southeastern corner of the Northern Territory to the northwestern edge of New South Wales, most of it is dry, desert landscape through which ephemeral streams lead to Lake Eyre, in the southwest corner of the Basin. Nearly dry and coated with salt flats most of the time, the lake fills only twice each Century (on average); composed of a large northern basin connected to a smaller southern basin by the Goyder Channel, Lake Eyre covers 3700 square miles and has an average depth of less than 10 feet (when full) The lowest point of the lake basin, in Belt Bay of the northern portion, is 50 feet below sea level while the rim of the lake is 30 feet below the level of the sea.
The Lake Eyre Basin began to form about 200 million years ago, when Australia was part of Gondwanaland. Tectonic forces caused the crust of this region to subside and, within another 100 million years, an arm of the sea invaded the basin; when uplift occurred along the northern and eastern margins of the basin, the sea drained away and rivers flowed across the region, depositing sediments on their way to the ocean. During the middle of the Pleistocene, about 1 million years ago, uplift along the southern rim closed off the basin and all streams fed Lake Diers, the much larger predecessor of Lake Eyre (as Lake Bonneville preceded the Great Salt Lake in the U.S.). As the climate became warmer and drier late in the Pleistocene and into the Holocene, the flow through the rivers diminished and eventually became sporadic. Today, what little water reaches the lake is via three primary river systems: the Georgina River from the north, the Diamantia River from the northeast and Cooper Creek from the east. Most streams from the west and northwest dry up before reaching Lake Eyre.
During those rare periods when monsoon rains or tropical storms fill Lake Eyre, this remote oasis attracts huge flocks of shorebirds, terns and Australian Pelicans that nest on the islands and feed in the shallows; how these birds know that the distant lake is full remains a mystery. Lake Eyre National Park stretches along the east shore of the northern lake, just a short 435 mile drive north from Adelaide. Major towns within the Lake Eyre Basin include Alice Springs, Mt. Isa, Longreach and Broken Hill.
Minggu, 17 Juni 2012
Glacial Lake Souris
Near the end of the Pleistocene, 10-15,000 years ago, large meltwater lakes formed along the retreating edge of the Continental Ice Sheet. One of these, Lake Souris, extended from north-central North Dakota into Manitoba, intermittently connecting with Glacial Lake Agassiz, to its east.
All of these lakes expanded and contracted depending upon their interconnections, the regional climate and the rate of meltwater production. Dammed by tongues of ice or moraines of glacial debris, some would occasionally break through their retaining wall, sending a torrent of water across the flat landscape of the Northern Plains. One such event involved Glacial Lake Regina of southern Saskatchewan, which flooded southeastward into Lake Souris; the broad, shallow channels of this flood remain evident today and are partly occupied by the Upper Souris River and its major tributary, the Des Lacs River.
East of Minot, the Souris River now enters the former lake bed of Glacial Lake Souris, following it north and gradually eastward to merge with the Assiniboine River of southern Manitoba; Lake Souris, itself, eventually drained into Lake Agassiz, which contracted into Lake Winnepeg after drainage opened to the north. National Wildlife Refuges now line the Des Lacs and Souris Rivers which, as we saw last summer, may still flood across the Pleistocene channels and lake beds when a deep winter snowpack is followed by heavy spring rains.
All of these lakes expanded and contracted depending upon their interconnections, the regional climate and the rate of meltwater production. Dammed by tongues of ice or moraines of glacial debris, some would occasionally break through their retaining wall, sending a torrent of water across the flat landscape of the Northern Plains. One such event involved Glacial Lake Regina of southern Saskatchewan, which flooded southeastward into Lake Souris; the broad, shallow channels of this flood remain evident today and are partly occupied by the Upper Souris River and its major tributary, the Des Lacs River.
East of Minot, the Souris River now enters the former lake bed of Glacial Lake Souris, following it north and gradually eastward to merge with the Assiniboine River of southern Manitoba; Lake Souris, itself, eventually drained into Lake Agassiz, which contracted into Lake Winnepeg after drainage opened to the north. National Wildlife Refuges now line the Des Lacs and Souris Rivers which, as we saw last summer, may still flood across the Pleistocene channels and lake beds when a deep winter snowpack is followed by heavy spring rains.
Sabtu, 16 Juni 2012
The Flathead River
The Flathead River of northwest Montana rises via three primary forks. The North Fork heads in the mountains of southeast British Columbia and then flows south along the western edge of Glacier National Park. The Middle Fork rises in the Rocky Mountains, northwest of Great Falls, winding northwest and then westward to join the North Fork. The South Fork also rises in the Rockies, more directly west of Great Falls, and flows NNW, where it enters Hungry Horse Reservoir before merging with the combined North and Middle Forks. The primary channel of the Flathead River then enters the Rocky Mountain Trench, a broad valley formed by downwarping of the crust as mountains rose to its east and later occupied by Pleistocene glaciers. Flowing southwestward and then southward, the river passes Kalispell, Montana, and enters Flathead Lake; the Stillwater, Whitefish and Swan Rivers also feed the lake.
The largest natural freshwater lake (by area) in the western Lower 48, Flathead Lake initially formed from glacial meltwater behind a terminal moraine that was deposited late in the Pleistocene; the lake valley was also inundated by Glacial Lake Missoula as it expanded and retreated 30-15,000 years ago (see my blog on 4-2-12). Exiting the southwest corner of its lake, the Flathead River snakes southward across a landscape of plateaus and ridges before flowing westward through a rugged canyon to join the Clark Fork River.
The upper forks of the Flathead have all been designated National Wild & Scenic Rivers and are among the most remote and least disturbed streams in our country. Nevertheless, the North Fork faced possible contamination from proposed coal mining and gas production in southeastern British Columbia over the past few decades; fortunately, an agreement between the U.S. and Canada has, for now, blocked that "development."
The largest natural freshwater lake (by area) in the western Lower 48, Flathead Lake initially formed from glacial meltwater behind a terminal moraine that was deposited late in the Pleistocene; the lake valley was also inundated by Glacial Lake Missoula as it expanded and retreated 30-15,000 years ago (see my blog on 4-2-12). Exiting the southwest corner of its lake, the Flathead River snakes southward across a landscape of plateaus and ridges before flowing westward through a rugged canyon to join the Clark Fork River.
The upper forks of the Flathead have all been designated National Wild & Scenic Rivers and are among the most remote and least disturbed streams in our country. Nevertheless, the North Fork faced possible contamination from proposed coal mining and gas production in southeastern British Columbia over the past few decades; fortunately, an agreement between the U.S. and Canada has, for now, blocked that "development."
Sabtu, 09 Juni 2012
Dry Rivers on the High Plains
Most of the rivers that cross the High Plains of the American West would hardly be recognized as creeks farther to the east. While the primary rivers that rise in the mountains, including the Missouri, Yellowstone, Platte and Arkansas Rivers deserve their title, many of the smaller rivers, heading on the High Plains Province itself, are dry for much of the year, transmitting water only after episodes of torrential rain or rapid snowmelt. Among these sandy channels are the upper tributaries of the Niobrara, Republican and Smokey Hill watersheds.
Cut off from Pacific moisture by the Continental Divide and located far from the Gulf of Mexico, the High Plains only receive copious precipitation when powerful storms draw in moisture laden air from the east, events that most often occur from February through June; indeed, this geophysical province receives less than 20 inches of precipitation each year. Yet, if we study the High Plains topography, we find that these meager conduits have managed to carve ridges, hills and valleys from the otherwise level plain, suggesting that they were more substantial streams in the past. In fact, during the Pleistocene Epoch (2 million to 10 thousand years ago) the regional climate was much cooler and wetter, giving rise to rivers that, in today's climate, have withered to channels of sand, prairie grass and scattered stands of cottonwood trees.
As with other ecosystems across our globe, it is impossible to understand the current geography without an appreciation for natural history and the region's underlying geology. In the case of the American High Plains, Pleistocene rivers sculpted the Tertiary deposits and underlying Cretaceous Sea sediments into the landscape that we find today; feeble and intermittent streams now occupy the valleys that those rivers left behind.
Cut off from Pacific moisture by the Continental Divide and located far from the Gulf of Mexico, the High Plains only receive copious precipitation when powerful storms draw in moisture laden air from the east, events that most often occur from February through June; indeed, this geophysical province receives less than 20 inches of precipitation each year. Yet, if we study the High Plains topography, we find that these meager conduits have managed to carve ridges, hills and valleys from the otherwise level plain, suggesting that they were more substantial streams in the past. In fact, during the Pleistocene Epoch (2 million to 10 thousand years ago) the regional climate was much cooler and wetter, giving rise to rivers that, in today's climate, have withered to channels of sand, prairie grass and scattered stands of cottonwood trees.
As with other ecosystems across our globe, it is impossible to understand the current geography without an appreciation for natural history and the region's underlying geology. In the case of the American High Plains, Pleistocene rivers sculpted the Tertiary deposits and underlying Cretaceous Sea sediments into the landscape that we find today; feeble and intermittent streams now occupy the valleys that those rivers left behind.
Minggu, 03 Juni 2012
American Creationists
This week, CNN reported on a recent survey of American adults that revealed almost half of us reject the concept of human evolution and believe that humans were created by God within the past 10,000 years; among Republicans, 60% hold this view. This large contingent of creationists is, to say the least, disturbing to those of us who accept the scientific method as the only legitimate means for solving the mysteries of the Universe and for defining our place within its vast realm.
The results of the survey suggest that two factors are at play. First, scientific education within the U.S. is woefully deficient, even among college-educated adults. Second, the influence of organized religion in America remains very powerful and, despite the copious scientific evidence that supports human evolution, many religious persons either choose to ignore that data or find the ancient, pre-scientific writings of early prophets more convincing. There is little doubt that religious beliefs, ingrained in childhood and sustained by fear and guilt, fuel distrust of science, as they have since the earliest days of human civilization.
The fact that we live on a small planet near the outer edge of a massive galaxy that is one of billions of galaxies in our Universe seems to have no bearing on their belief; neither does the evidence that the Universe is 13.7 billion years old, that Earth is 4.6 billion years old and that life has colonized our planet for 3.6 billion years. If the creationists are correct, God is a very patient deity indeed.
The results of the survey suggest that two factors are at play. First, scientific education within the U.S. is woefully deficient, even among college-educated adults. Second, the influence of organized religion in America remains very powerful and, despite the copious scientific evidence that supports human evolution, many religious persons either choose to ignore that data or find the ancient, pre-scientific writings of early prophets more convincing. There is little doubt that religious beliefs, ingrained in childhood and sustained by fear and guilt, fuel distrust of science, as they have since the earliest days of human civilization.
The fact that we live on a small planet near the outer edge of a massive galaxy that is one of billions of galaxies in our Universe seems to have no bearing on their belief; neither does the evidence that the Universe is 13.7 billion years old, that Earth is 4.6 billion years old and that life has colonized our planet for 3.6 billion years. If the creationists are correct, God is a very patient deity indeed.
Rabu, 30 Mei 2012
Italy, Earthquakes & Human Nature
After enduring two tragic earthquakes within a span of nine days, residents of northeastern Italy are both distraught and mystified. As emphasized in news reports, that region had not experienced a significant earthquake for hundreds of years. Yet, this industrial valley stretches between the Apennines and the Alps, mountain ranges that owe their very existence to the collision of the African and Eurasian Plates.
This tectonic collision, though too gradual to witness during our brief life span, has been going on for at least 40 million years, producing the varied landscape of southern Europe. A quiescent period of seismic activity in any given area, even lasting hundreds or thousands of years, is to be expected as pressure along the collision zone shifts from one region to another. While we may understand the geologic cause for the earthquakes, our inability to accurately predict the timing of such events has become all too clear over the past few decades; nevertheless, scientists in Italy are facing manslaughter charges for their failure to predict the 2009 quake in the Apennines, east of Rome, which killed more than 300 citizens.
We humans have a tendency to blame others for the misfortunes that we endure, even when they arise from the uncontrollable and, to date, unpredictable natural forces that mold our planet. We also tend to interpret our Universe, distant galaxies or local geography, from the narrow perspective of our human life span. Anyone who resides along the active plate margins of Planet Earth cannot afford to ignore the realities of its past and ongoing geologic evolution, however remote the risk of catastrophe might seem at the present time. After all, the Africa-Eurasian collision has been underway for 40 million years, 400 times longer than our own species has walked the planet.
This tectonic collision, though too gradual to witness during our brief life span, has been going on for at least 40 million years, producing the varied landscape of southern Europe. A quiescent period of seismic activity in any given area, even lasting hundreds or thousands of years, is to be expected as pressure along the collision zone shifts from one region to another. While we may understand the geologic cause for the earthquakes, our inability to accurately predict the timing of such events has become all too clear over the past few decades; nevertheless, scientists in Italy are facing manslaughter charges for their failure to predict the 2009 quake in the Apennines, east of Rome, which killed more than 300 citizens.
We humans have a tendency to blame others for the misfortunes that we endure, even when they arise from the uncontrollable and, to date, unpredictable natural forces that mold our planet. We also tend to interpret our Universe, distant galaxies or local geography, from the narrow perspective of our human life span. Anyone who resides along the active plate margins of Planet Earth cannot afford to ignore the realities of its past and ongoing geologic evolution, however remote the risk of catastrophe might seem at the present time. After all, the Africa-Eurasian collision has been underway for 40 million years, 400 times longer than our own species has walked the planet.
Rabu, 23 Mei 2012
Sediments, Fossils & Time
Amateur naturalists are often confused by the distribution of fossils across our globe, wondering why certain fossils (of dinosaurs, for example) are plentiful in some areas but absent in others. In general, the fossils of plants and animals result from their remains having been trapped within sediment (lake deposits, ocean floor sediment, river mud, volcanic debris, etc.) that, over millions of years, hardened into sandstone, mudstone, limestone or some other sedimentary rock. Of course, most animals and plants die under circumstances in which their remains are consumed, undergo decay or are scattered by predators and natural forces before such fossilization can occur.
The type of fossils present in any region of our planet depends upon the age of the exposed sedimentary rocks in that area; rocks that formed from sediments that accumulated during any given geologic era will harbor fossils of life from that era. The exposure of these sedimentary rocks is a product of regional uplift, erosion and the deposition of overlying sediments (not necessarily occuring in that order). For example, Jurassic sedimentary rock, which accumulated during the Age of Dinosaurs, may have been lifted to the surface (as in large parts of the American West), may be buried deep beneath younger sediments or may have long-since eroded from the surface due to action of streams or glaciers; in other areas, these sediments may have never accumulated in the first place due to regional topography throughout the Jurassic Period.
Millions of years from now, Holocene sedimentary rocks will be explored by our super-human decendants or, perhaps, by visitors from other solar systems. Encased in those rocks will be the fossils of human civilization, including our domestic livestock, our cultivated plants, our pet poodles and the plants and animals that comprise our natural ecosystems. These Holocene sediments may be found deep in canyons, atop mountain ranges or outcropping from desert plains; in many areas they will lie deep beneath the fossilized remnants of younger civilizations while, in others, they will have already washed away to the sea.
The type of fossils present in any region of our planet depends upon the age of the exposed sedimentary rocks in that area; rocks that formed from sediments that accumulated during any given geologic era will harbor fossils of life from that era. The exposure of these sedimentary rocks is a product of regional uplift, erosion and the deposition of overlying sediments (not necessarily occuring in that order). For example, Jurassic sedimentary rock, which accumulated during the Age of Dinosaurs, may have been lifted to the surface (as in large parts of the American West), may be buried deep beneath younger sediments or may have long-since eroded from the surface due to action of streams or glaciers; in other areas, these sediments may have never accumulated in the first place due to regional topography throughout the Jurassic Period.
Millions of years from now, Holocene sedimentary rocks will be explored by our super-human decendants or, perhaps, by visitors from other solar systems. Encased in those rocks will be the fossils of human civilization, including our domestic livestock, our cultivated plants, our pet poodles and the plants and animals that comprise our natural ecosystems. These Holocene sediments may be found deep in canyons, atop mountain ranges or outcropping from desert plains; in many areas they will lie deep beneath the fossilized remnants of younger civilizations while, in others, they will have already washed away to the sea.
Rabu, 09 Mei 2012
The Eurasian Mountain Arc
Looking at a map of Earth, one sees a complex of mountain ranges from Southeast Asia to Spain. Almost all of these ranges are relatively young, having crumpled skyward throughout the Tertiary Period; in fact, all are still rising today, a fact made evident by frequent earthquakes across this swath of landscape.
About 55 million years ago (MYA), soon after the Rocky Mountains formed in North America, the Indian Subcontinent began to collide with southern Asia, forcing up the Himalayas and its associated ranges, from southern China to Afghanistan. By 40 MYA, the Red Sea and Gulf of Aden began to open, splitting the Arabian Plate from Africa and pushing it northward into southwestern Asia; this compressed the crust of that region, lifting the ranges of Iran, eastern Turkey and the Middle East. About the same time, as the Tethys Sea was closing, Africa drifted northward to collide with southern Europe; this has crumpled up the Alps and its associated ranges, from western Turkey and Greece to the Pyrenees of Spain. In concert, regional subduction of the African Plate beneath the Eurasian Plate has produced a chain of volcanos along the western edge of Italy.
In some areas, such as the Pyrenees, older mountain ranges, having eroded to low hills, were renewed by these Tertiary orogenies. Today, as these tectonic forces persist and the "new" mountains continue to rise, the agents of erosion combat their uplift; molded by glaciers and incised by streams, their rock dust is carried off to the sea where, millions of years in the future, it may resurface as the core of another mountain range.
About 55 million years ago (MYA), soon after the Rocky Mountains formed in North America, the Indian Subcontinent began to collide with southern Asia, forcing up the Himalayas and its associated ranges, from southern China to Afghanistan. By 40 MYA, the Red Sea and Gulf of Aden began to open, splitting the Arabian Plate from Africa and pushing it northward into southwestern Asia; this compressed the crust of that region, lifting the ranges of Iran, eastern Turkey and the Middle East. About the same time, as the Tethys Sea was closing, Africa drifted northward to collide with southern Europe; this has crumpled up the Alps and its associated ranges, from western Turkey and Greece to the Pyrenees of Spain. In concert, regional subduction of the African Plate beneath the Eurasian Plate has produced a chain of volcanos along the western edge of Italy.
In some areas, such as the Pyrenees, older mountain ranges, having eroded to low hills, were renewed by these Tertiary orogenies. Today, as these tectonic forces persist and the "new" mountains continue to rise, the agents of erosion combat their uplift; molded by glaciers and incised by streams, their rock dust is carried off to the sea where, millions of years in the future, it may resurface as the core of another mountain range.
Sabtu, 28 April 2012
The Illinois Basin
Like the Michigan and Permian Basins, the Illinois Basin is a structural bowl of Precambrian basement rock within which younger layers of sedimentary rock have accumulated. This bowl, which covers the southern 75% of Illinois, the southwestern 40% of Indiana, western Kentucky and a small portion of northwest Tennessee, is surrounded by structural "arches," uplifts of the deep, ancient Precambrian rock; these include the Kankakee Arch to the northeast, the Cincinnati Arch to the southeast, the Wisconsin Arch to the north, the Mississippi River Arch to the northwest, the Ozark Uplift to the west and the Pascola Arch to the southwest.
Three miles deep at its center, this broad basin of Precambrian rock, 1.3 billion years old, accumulated layers of sediment throughout much of the Paleozoic Era (from 600 to 270 million years ago); the great majority of these deposits occured within shallow seas, which invaded and retreated from the basin at least 50 times during that period, while others were carried in by streams or deposited within vast wetlands. As the basin filled in from the Cambrian to the Pennsylvanian Periods, these layers of sediment dipped from the surrounding arches toward the center of the structural depression; at the surface, older sediments are thus found at the periphery of the basin while the youngest (Pennsylvanian) cover its center. Following this prolonged period of deposition, which was intermittently disrupted by uplift and erosion, the Illinois Basin has undergone surface molding by the Pleistocene Glaciers and numerous streams; the glaciers flattened northern portions of the basin and coated them with a thick layer of glacial till while streams have carved southern portions into a maze of hills and valleys.
Travelling across the Illinois Basin today, one sees no evidence of the Precambrian bowl that underlies the region; indeed, its edge only outcrops in limited areas of southern Wisconsin and southeastern Missouri. Glacial erosion and till have produced the flat, productive Corn Belt across much of Illinois and western Indiana while Carboniferous sediments of the basin have been mined for their coal and drilled for their oil. As in most regions of our globe, the surface topography of the Illinois Basin only hints at the miles of sediment and complex geologic formations that lie below.
Three miles deep at its center, this broad basin of Precambrian rock, 1.3 billion years old, accumulated layers of sediment throughout much of the Paleozoic Era (from 600 to 270 million years ago); the great majority of these deposits occured within shallow seas, which invaded and retreated from the basin at least 50 times during that period, while others were carried in by streams or deposited within vast wetlands. As the basin filled in from the Cambrian to the Pennsylvanian Periods, these layers of sediment dipped from the surrounding arches toward the center of the structural depression; at the surface, older sediments are thus found at the periphery of the basin while the youngest (Pennsylvanian) cover its center. Following this prolonged period of deposition, which was intermittently disrupted by uplift and erosion, the Illinois Basin has undergone surface molding by the Pleistocene Glaciers and numerous streams; the glaciers flattened northern portions of the basin and coated them with a thick layer of glacial till while streams have carved southern portions into a maze of hills and valleys.
Travelling across the Illinois Basin today, one sees no evidence of the Precambrian bowl that underlies the region; indeed, its edge only outcrops in limited areas of southern Wisconsin and southeastern Missouri. Glacial erosion and till have produced the flat, productive Corn Belt across much of Illinois and western Indiana while Carboniferous sediments of the basin have been mined for their coal and drilled for their oil. As in most regions of our globe, the surface topography of the Illinois Basin only hints at the miles of sediment and complex geologic formations that lie below.
Senin, 02 April 2012
Lake Missoula & the Channeled Scablands
Near the end of the Pleistocene Ice Age, about 13,000 years ago, a lobe of the Cordilleran Glacier that covered the Rocky Mountains blocked the flow of the Clark Fork River, in northwestern Montana. Behind this dam of ice, a massive lake developed; 200 miles long and 2000 feet deep, Glacial Lake Missoula contained 500 cubic miles of glacial meltwater.
Eventually, the ice dam failed and a torrent of water rushed across the Idaho Panhandle, eastern Washington and the Columbia River Valley. In fact, as the glacier advanced and retreated over 2500 years, the lake repeatedly formed and drained, eroding the Channeled Scablands of the Columbia Plateau. Characterized by broad, braided canyons, dry falls, rippled rock formations, massive gravel bars and countless erratic boulders, this unique topography attests to the power of the recurrent floods; indeed, the Columbia River Gorge was primarily carved by these torrents.
While similar glacial lake floods occured elsewhere across the Northern Hemisphere (including the Bonneville Flood of southern Idaho), none were as powerful as those arising from Lake Missoula. Geologists and hydrologists estimate that the flow of these deluge events (which numbered three dozen or more) exceeded the current total flow of all rivers on Earth and emptied the Lake within a few days.
Eventually, the ice dam failed and a torrent of water rushed across the Idaho Panhandle, eastern Washington and the Columbia River Valley. In fact, as the glacier advanced and retreated over 2500 years, the lake repeatedly formed and drained, eroding the Channeled Scablands of the Columbia Plateau. Characterized by broad, braided canyons, dry falls, rippled rock formations, massive gravel bars and countless erratic boulders, this unique topography attests to the power of the recurrent floods; indeed, the Columbia River Gorge was primarily carved by these torrents.
While similar glacial lake floods occured elsewhere across the Northern Hemisphere (including the Bonneville Flood of southern Idaho), none were as powerful as those arising from Lake Missoula. Geologists and hydrologists estimate that the flow of these deluge events (which numbered three dozen or more) exceeded the current total flow of all rivers on Earth and emptied the Lake within a few days.
Selasa, 27 Maret 2012
Future Exotic Terranes
The continents of planet Earth are composed of central, "stable" platforms to which smaller "exotic terranes" have accreted and from which other segments of crust have rifted away. In fact, the central platforms (or cratons) are, themselves, composed of ancient segments that fused together early in geologic history and possess aborted rift zones that could reactivate in the future.
Exotic terranes are segments of continental crust that either rifted from a larger land mass or formed above oceanic hotspots, mid-oceanic ridges or subduction zones as volcanic islands. Moving with the surrounding oceanic crust, they accrete to another continent where the intervening oceanic crust subducts into a trench. Looking at the current geologic map of our planet, we can thus identify land masses that will become exotic terranes in the future (as long as the current plate movements and subduction zones do not change).
Examples include Southern California and the Baja Peninsula, which are moving NNW with the Pacific Plate toward the Aleutian Chain of Alaska, the Hawaiian Islands, which are moving toward the Kamchatka Peninsula of Siberia, and the Galapagos Islands, which are moving eastward on the Nazca Plate toward Ecuador. If the East African Rift continues to develop, southeastern Africa will become a large exotic terrane that could swivel northeastward to join India or might drift eastward and attach to Southeast Asia. Of course, all of these projections will be wrong if the current oceanic spreading zones shut down or if new continental rifts develop; we should find out in 80 million years or so.
Exotic terranes are segments of continental crust that either rifted from a larger land mass or formed above oceanic hotspots, mid-oceanic ridges or subduction zones as volcanic islands. Moving with the surrounding oceanic crust, they accrete to another continent where the intervening oceanic crust subducts into a trench. Looking at the current geologic map of our planet, we can thus identify land masses that will become exotic terranes in the future (as long as the current plate movements and subduction zones do not change).
Examples include Southern California and the Baja Peninsula, which are moving NNW with the Pacific Plate toward the Aleutian Chain of Alaska, the Hawaiian Islands, which are moving toward the Kamchatka Peninsula of Siberia, and the Galapagos Islands, which are moving eastward on the Nazca Plate toward Ecuador. If the East African Rift continues to develop, southeastern Africa will become a large exotic terrane that could swivel northeastward to join India or might drift eastward and attach to Southeast Asia. Of course, all of these projections will be wrong if the current oceanic spreading zones shut down or if new continental rifts develop; we should find out in 80 million years or so.
Selasa, 20 Maret 2012
The Caspian Sea
A remnant of the Paratethys Sea, the Caspian Sea is the largest inland body of water on Earth. Covering more than 143,000 square miles, it was cut off from the Black Sea when the Caucasus Mountains rose some 6 million years ago, a product of the Red Sea opening which forced (and continues to force) the Arabian Plate to collide with the Eurasian Plate. Retaining some salinity from the Paratethys, the Caspian Sea has become a massive basin lake, receiving inflow from more than 130 freshwater rivers but having no outlet to the sea; 80% of the inflow is via the Volga River while the combined flow of the Ural and Kura Rivers adds another 15%.
Since this inflow is primarily from the north and northwest shores of the Caspian Sea, its relatively shallow northern waters (only 20 feet deep) are fresh while the deeper waters of its southern section (exceeding 3000 feet in some areas) have a salinity that is 1/3 of that found in our oceans. Kara-Bogaz-Gol, a large lagoon on its eastern shore (within Turkmenistan) has been nearly cutoff by sandbars and receives inflow only during periods of high water in the Caspian Sea; the lagoon's waters, subject to intense evaporation, have a salinity that is 10 times that of sea water. Today, five countries border the Caspian Sea: Russia on the northwest, Kazakhstan on the northeast, Azerbaijan on the southwest, Turkmenistan on the southeast and Iran on the south; except for the Caspian Depression to its north, the Caspian Sea is rimmed by highlands and its surface elevation, while variable, is about 92 feet below sea level.
While lush wetlands are spaced along its western and southern shores, the Caspian Sea is bordered by desert on its northern and eastern coasts; of special interest is a region of geothermal mud domes along part of the Azerbaijan coast, a testament to plate subduction in that area. Famous for a magnificent diversity of birdlife (especially during migrations), its prized sturgeon caviar and its endemic Caspian seals (thought to have arrived when the Paratethys connected to the North Sea), this unique and varied ecosystem is threatened by both global warming and industrial pollution (especially from oil and gas production). Since it is rimmed by five countries, the effort to protect this ecological treasure is especially challenging.
Since this inflow is primarily from the north and northwest shores of the Caspian Sea, its relatively shallow northern waters (only 20 feet deep) are fresh while the deeper waters of its southern section (exceeding 3000 feet in some areas) have a salinity that is 1/3 of that found in our oceans. Kara-Bogaz-Gol, a large lagoon on its eastern shore (within Turkmenistan) has been nearly cutoff by sandbars and receives inflow only during periods of high water in the Caspian Sea; the lagoon's waters, subject to intense evaporation, have a salinity that is 10 times that of sea water. Today, five countries border the Caspian Sea: Russia on the northwest, Kazakhstan on the northeast, Azerbaijan on the southwest, Turkmenistan on the southeast and Iran on the south; except for the Caspian Depression to its north, the Caspian Sea is rimmed by highlands and its surface elevation, while variable, is about 92 feet below sea level.
While lush wetlands are spaced along its western and southern shores, the Caspian Sea is bordered by desert on its northern and eastern coasts; of special interest is a region of geothermal mud domes along part of the Azerbaijan coast, a testament to plate subduction in that area. Famous for a magnificent diversity of birdlife (especially during migrations), its prized sturgeon caviar and its endemic Caspian seals (thought to have arrived when the Paratethys connected to the North Sea), this unique and varied ecosystem is threatened by both global warming and industrial pollution (especially from oil and gas production). Since it is rimmed by five countries, the effort to protect this ecological treasure is especially challenging.
Rabu, 14 Maret 2012
Geophysical Provinces of Ohio
Though known primarily for its rolling farmlands, Ohio is a mosaic of geophysical provinces, defined by underlying geology, tectonic uplift and the erosive power of Pleistocene Glaciers. From a broad perspective, the State overlaps two major provinces; the northwestern 60% of Ohio lies within the Central Lowlands of North America while the southeastern 40% is occupied by the Appalachian Plateau. The border between these two geophysical regions runs SSW, from the northeast corner of Ohio to the Ohio River Valley at the southern edge of the State.
The Appalachian Plateau, composed of Carboniferous sandstones, limestones and shales, was lifted with the Southern Appalachian Mountains as North America and Africa collided during the formation of Pangea, some 300 million years ago. While the Plateau's western edge has been obscured by glacial erosion in northeastern Ohio, it stands out as a prominent escarpment through the southern half of the State, rising 500 feet above the adjacent lowlands. The Central Lowlands within Ohio are comprised of four sub-provinces: the Lake Plain, the Glacial Till Plains, the Ohio Valley and a small segment of the Interior Low Plateaus; the latter, unglaciated province, characterized by glades and karst landscapes, extends from Adams County, in southwestern Ohio, southward and then westward through Kentucky, western Tennessee, southern Indiana and southern Illinois.
The Lake Plain of northern Ohio is a swath of flat terrain south of Lake Erie, representing the post-glacial extent of Lake Warren, Lake Erie's larger predecessor; it is underlain with Devonian sedimentary rocks which have since been covered by glacial till and sandy lake deposits (though these rocks are exposed along the Lake Erie shoreline, in major river valleys and on Ohio's Lake Erie islands). South of the Lake Plain, the gently rolling farmlands of central and west-central Ohio occupy the Till Plains, molded by a number of post-glacial streams that flow southward to the Ohio River; beneath the thick layer of till are Silurian (western Ohio) and Devonian (central Ohio) sedimentary rocks, deposited in shallow seas from 400-350 million years ago. Finally, in the southwest corner of Ohio, ancient Ordovician limestones and shales, 500 million years old, have been sculpted into the hilly terrain of Greater Cincinnati by the erosive force of glacial meltwater and the continued action of post-glacial streams; harboring fossils of trilobites, brachiopods and other early marine invertebrates, these are the oldest exposed rocks in the State.
The Appalachian Plateau, composed of Carboniferous sandstones, limestones and shales, was lifted with the Southern Appalachian Mountains as North America and Africa collided during the formation of Pangea, some 300 million years ago. While the Plateau's western edge has been obscured by glacial erosion in northeastern Ohio, it stands out as a prominent escarpment through the southern half of the State, rising 500 feet above the adjacent lowlands. The Central Lowlands within Ohio are comprised of four sub-provinces: the Lake Plain, the Glacial Till Plains, the Ohio Valley and a small segment of the Interior Low Plateaus; the latter, unglaciated province, characterized by glades and karst landscapes, extends from Adams County, in southwestern Ohio, southward and then westward through Kentucky, western Tennessee, southern Indiana and southern Illinois.
The Lake Plain of northern Ohio is a swath of flat terrain south of Lake Erie, representing the post-glacial extent of Lake Warren, Lake Erie's larger predecessor; it is underlain with Devonian sedimentary rocks which have since been covered by glacial till and sandy lake deposits (though these rocks are exposed along the Lake Erie shoreline, in major river valleys and on Ohio's Lake Erie islands). South of the Lake Plain, the gently rolling farmlands of central and west-central Ohio occupy the Till Plains, molded by a number of post-glacial streams that flow southward to the Ohio River; beneath the thick layer of till are Silurian (western Ohio) and Devonian (central Ohio) sedimentary rocks, deposited in shallow seas from 400-350 million years ago. Finally, in the southwest corner of Ohio, ancient Ordovician limestones and shales, 500 million years old, have been sculpted into the hilly terrain of Greater Cincinnati by the erosive force of glacial meltwater and the continued action of post-glacial streams; harboring fossils of trilobites, brachiopods and other early marine invertebrates, these are the oldest exposed rocks in the State.
Selasa, 13 Maret 2012
Black Squirrels
Having lived among gray tree squirrels and golden-brown fox squirrels throughout my life, I am always caught off guard when I re-encounter the black squirrels of northeastern Ohio during visits to my wife's home town. These melanistic variants of eastern gray squirrels are not isolated mutants but, rather, represent the dominant phenotype of their species.
When European explorers and settlers first arrived in North America, almost all eastern gray squirrel populations were reported to be black in color. Thought to have evolved as camouflage from predators when these agile creatures inhabited the dark, mature forests of the eastern U.S. and eastern Canada, the coloration has shifted to gray or gray-brown in the open forests, woodlots and suburban areas that characterize most regions today. Nevertheless, the black race of eastern gray squirrels remains dominant in many areas of the Northeast, from southern Canada to northeastern Ohio and northern Pennsylvania and from Michigan to New England. In some areas, eastern gray squirrels may harbor a mixed coat of gray-brown, black and white.
In all other respects, these racial variants manifest the same behavior and arboreal lifestyle and, as members of the same species, they are able to interbreed; their variable coloration merely reflects the outward expression of their genome (as does the hair color and skin tone of humans). Sexual reproduction ensures a serial mixing of their genes and, over many generations, natural selection determines the physical appearance of regional squirrel populations, retaining traits that favor survival within each ecosystem.
When European explorers and settlers first arrived in North America, almost all eastern gray squirrel populations were reported to be black in color. Thought to have evolved as camouflage from predators when these agile creatures inhabited the dark, mature forests of the eastern U.S. and eastern Canada, the coloration has shifted to gray or gray-brown in the open forests, woodlots and suburban areas that characterize most regions today. Nevertheless, the black race of eastern gray squirrels remains dominant in many areas of the Northeast, from southern Canada to northeastern Ohio and northern Pennsylvania and from Michigan to New England. In some areas, eastern gray squirrels may harbor a mixed coat of gray-brown, black and white.
In all other respects, these racial variants manifest the same behavior and arboreal lifestyle and, as members of the same species, they are able to interbreed; their variable coloration merely reflects the outward expression of their genome (as does the hair color and skin tone of humans). Sexual reproduction ensures a serial mixing of their genes and, over many generations, natural selection determines the physical appearance of regional squirrel populations, retaining traits that favor survival within each ecosystem.
Kamis, 08 Maret 2012
Mono Lake
Mono Lake is a 70 square-mile saline lake at the eastern foot of the Sierra Nevada Range, approximately 13 miles east of Yosemite National Park. Enclosed within a natural basin by the Sierra Batholith to its west and Pliocene-Pleistocene volcanic ranges to its north, east and south, the lake is fed by three primary streams (Lee Vining, Rush and Mill Creeks) and by freshwater springs along its floor. Having formed during the Pleistocene, about 1 million years ago, it is one of the oldest lakes in North America and is the largest lake completely within California.
As a basin lake, its size and depth are a balance between inflow from streams and springs and evaporative loss in the dry climate of the Basin and Range Province. Prior to 1941, its surface elevation hovered above 6400 feet but this was dramatically lowered by diversion of inflow to the Los Angeles Water System; legal challenges by conservation groups eventually restored most of the inflow by 1994.
Despite its high salinity (2.5 times that of ocean water) and alkalinity (which precludes fish survival), Mono Lake supports a spectacular ecosystem. Photosynthetic algae, feeding on minerals from the surrounding mountains, bloom in spring when snowmelt peaks. Feeding on the algae, brine shrimp and brine flies thrive in the lake shallows and provide vital nourishment for migrating shorebirds, eared grebes and phalaropes, among other species; indeed, Mono Lake was added to the Western Hemisphere Shorebird Reserve Network in 1991. California gulls and snowy plovers nest on Paoha Island and smaller islets, escaping predation by fox and coyotes. Beyond the abundant birdlife, Mono Lake is perhaps best known for its tufa towers of calcium carbonate, produced by the interaction of freshwater springs and the alkaline, mineral-rich lake waters. Students of geology will also appreciate the surrounding volcanic landscape, including the relatively recent Panum and Mono-Inyo craters, south of Mono Lake.
As a basin lake, its size and depth are a balance between inflow from streams and springs and evaporative loss in the dry climate of the Basin and Range Province. Prior to 1941, its surface elevation hovered above 6400 feet but this was dramatically lowered by diversion of inflow to the Los Angeles Water System; legal challenges by conservation groups eventually restored most of the inflow by 1994.
Despite its high salinity (2.5 times that of ocean water) and alkalinity (which precludes fish survival), Mono Lake supports a spectacular ecosystem. Photosynthetic algae, feeding on minerals from the surrounding mountains, bloom in spring when snowmelt peaks. Feeding on the algae, brine shrimp and brine flies thrive in the lake shallows and provide vital nourishment for migrating shorebirds, eared grebes and phalaropes, among other species; indeed, Mono Lake was added to the Western Hemisphere Shorebird Reserve Network in 1991. California gulls and snowy plovers nest on Paoha Island and smaller islets, escaping predation by fox and coyotes. Beyond the abundant birdlife, Mono Lake is perhaps best known for its tufa towers of calcium carbonate, produced by the interaction of freshwater springs and the alkaline, mineral-rich lake waters. Students of geology will also appreciate the surrounding volcanic landscape, including the relatively recent Panum and Mono-Inyo craters, south of Mono Lake.
Selasa, 06 Maret 2012
The Domestication of Animals
We humans have been domesticating animals for the past 12,000 years and they have played a crucial role in the rise of our civilization and in the formation of our varied cultures. We have used and abused animals for food, clothing, transportation, muscle power, laboratory experimentation, pollination, recreation and companionship.
Dogs were the first animals to be domesticated, used by clans of the Middle East for protection and hunting assistance some 12,000 years ago. Goats were domesticated in the Fertile Crescent about 10,000 years ago while sheep and pigs were raised in Turkey and Syria by 9000 years ago. About 8000 years ago, cattle were domesticated in Northern Africa and India, cats joined the households of Egypt and chickens were bred for eggs and meat in Southeast Asia. As the horse was domesticated by tribes of central Asia, some 6000 years ago, the Incas were utilizing llamas in the Andes of South America and donkeys were brought under human rule in Northern Africa, soon to be joined by camel caravans. Ducks were raised in Southeast Asia by 5000 years ago, guinea pigs were domesticated in the Andes 4500 years ago and elephants were pressed into service in India about 4000 years ago. Caribou were domesticated across the Arctic about 3000 years ago, turkeys were raised in Mexico 2000 years ago, honey bees were brought under control in Europe 1500 years ago, goldfish were farmed in China 1000 years ago and rabbits were domesticated in Europe by 500 years ago.
Looking at our pampered dogs and cats, better fed than many human populations, we sometimes glorify our relationship with the other animals that share this planet. Yet, as vital as many have been to the survival of our species, we have not often treated them with the dignity that they deserve. The abuse of animals on industrialized farms and in scientific labs has been a blight on our culture and must be addressed if we are to earn our self-proclaimed title of Earth's stewards.
Dogs were the first animals to be domesticated, used by clans of the Middle East for protection and hunting assistance some 12,000 years ago. Goats were domesticated in the Fertile Crescent about 10,000 years ago while sheep and pigs were raised in Turkey and Syria by 9000 years ago. About 8000 years ago, cattle were domesticated in Northern Africa and India, cats joined the households of Egypt and chickens were bred for eggs and meat in Southeast Asia. As the horse was domesticated by tribes of central Asia, some 6000 years ago, the Incas were utilizing llamas in the Andes of South America and donkeys were brought under human rule in Northern Africa, soon to be joined by camel caravans. Ducks were raised in Southeast Asia by 5000 years ago, guinea pigs were domesticated in the Andes 4500 years ago and elephants were pressed into service in India about 4000 years ago. Caribou were domesticated across the Arctic about 3000 years ago, turkeys were raised in Mexico 2000 years ago, honey bees were brought under control in Europe 1500 years ago, goldfish were farmed in China 1000 years ago and rabbits were domesticated in Europe by 500 years ago.
Looking at our pampered dogs and cats, better fed than many human populations, we sometimes glorify our relationship with the other animals that share this planet. Yet, as vital as many have been to the survival of our species, we have not often treated them with the dignity that they deserve. The abuse of animals on industrialized farms and in scientific labs has been a blight on our culture and must be addressed if we are to earn our self-proclaimed title of Earth's stewards.
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