Greater sage grouse, the largest grouse in North America, inhabit sage grasslands of the Intermountain West, from Colorado to the Columbia Plateau and from southern Alberta to southern Utah. Closely tied to their habitat, these grouse feed solely on the sage plant in the winter while supplementing that diet with a variety of forbs, insects and grasses during the warmer months. Unlike many game birds, they do not possess a muscular crop and cannot digest hard seeds.
Come spring, sage grouse gather in clearings (known as leks) at dawn and dusk, where the dominant males attract mates with ritualized strutting, tail fanning and a variety of noises from their air sacs; most of the females mate with only one or two of the performers. Nests are placed on the ground and females are solely responsible for both incubation and protection of the young; six to twelve eggs are generally produced. Able to forage soon after birth, the young are vulnerable to a wide range of predators, including snakes, prairie falcons, crows, magpies, badgers, coyotes, bobcats and owls.
Once abundant across the American West, greater sage grouse have long been threatened by habitat loss; their population, estimated to have been about 16 million in the early 1900s, has fallen to less than 500,000 today, a drop of 97% over the past century. The loss of sage grasslands to mining, ranching and oil production has been primarily responsible for this decline and efforts to list the greater sage grouse as an Endangered Species have been successfully blocked by Western Governors and their Federal colleagues. Perhaps a 99% population decline will be more convincing.
Tampilkan postingan dengan label Wyoming. Tampilkan semua postingan
Tampilkan postingan dengan label Wyoming. Tampilkan semua postingan
Selasa, 24 April 2012
Jumat, 18 November 2011
The Two-Basin River
As soon as the Rocky Mountains crumpled skyward, 70 million years ago (MYA), erosional debris began to fill the valleys and basins between the ranges. This process continued throughout most of the Tertiary Period and, by the Miocene (20 MYA), the terrain across this mountain corridor was relatively flat. A second uplift of the region, from the late Miocene into the Pliocene, followed by the wet climate of the Pleistocene, spawned river systems which uncovered the ranges and scoured out the intervening valleys and basins.
One of these streams was the Wind River of central Wyoming which rose along the east flank of the Wind River range, flowed to the southeast and then turned northward, eventually entering the Yellowstone River in southeast Montana. En route, this river crossed two buried ridges, the Owl Creek Mountains of central Wyoming and the Pryor Mountains along the Wyoming-Montana line; with its course set in the overlying Tertiary sediments, the Wind River carved spectacular canyons through these walls of rock, now known, respectively, as Wind River Canyon and Bighorn Canyon. Since the strata of these east-west ridges were tilted during uplift and faulting, the river exposed rock layers stretching from the Precambrian to the Mesozoic; in Wind River Canyon, the oldest layer, Precambrian granite dating back almost 3 billion years, towers along the canyon's southern mouth while Triassic redbeds, deposited 225 MYA, adorn the canyon at its north entrance.
Today, the original Wind River crosses two major topographic basins (the Wind River and Bighorn Basins), separated by the Owl Creek Mountains; north of Wind River Canyon, the river is now known as the Bighorn River. The Wind River Basin is bordered by the Wind River Range on its west, the Owl Creek Mountains on its north, the southern end of the Bighorn Range on its east and a low divide along its southern edge, separating the Wind River watershed from that of the Sweetwater River. After leaving Boysen Reservoir and flowing northward through Wind River Canyon in the Owl Creek Mountains, the Wind River enters Bighorn Basin and becomes the Bighorn River; the Bighorn Basin is bordered by the Absaroka Range on its west (composed of Eocene volcanic rocks), the Owl Creek Mountains on its south and the Bighorn Range on its east. At the north end of the basin the Bighorn River cuts through the Pryor Mountains to form Bighorn Canyon (described above) and then enters the Yellowstone River, a major tributary of the Missouri.
One of these streams was the Wind River of central Wyoming which rose along the east flank of the Wind River range, flowed to the southeast and then turned northward, eventually entering the Yellowstone River in southeast Montana. En route, this river crossed two buried ridges, the Owl Creek Mountains of central Wyoming and the Pryor Mountains along the Wyoming-Montana line; with its course set in the overlying Tertiary sediments, the Wind River carved spectacular canyons through these walls of rock, now known, respectively, as Wind River Canyon and Bighorn Canyon. Since the strata of these east-west ridges were tilted during uplift and faulting, the river exposed rock layers stretching from the Precambrian to the Mesozoic; in Wind River Canyon, the oldest layer, Precambrian granite dating back almost 3 billion years, towers along the canyon's southern mouth while Triassic redbeds, deposited 225 MYA, adorn the canyon at its north entrance.
Today, the original Wind River crosses two major topographic basins (the Wind River and Bighorn Basins), separated by the Owl Creek Mountains; north of Wind River Canyon, the river is now known as the Bighorn River. The Wind River Basin is bordered by the Wind River Range on its west, the Owl Creek Mountains on its north, the southern end of the Bighorn Range on its east and a low divide along its southern edge, separating the Wind River watershed from that of the Sweetwater River. After leaving Boysen Reservoir and flowing northward through Wind River Canyon in the Owl Creek Mountains, the Wind River enters Bighorn Basin and becomes the Bighorn River; the Bighorn Basin is bordered by the Absaroka Range on its west (composed of Eocene volcanic rocks), the Owl Creek Mountains on its south and the Bighorn Range on its east. At the north end of the basin the Bighorn River cuts through the Pryor Mountains to form Bighorn Canyon (described above) and then enters the Yellowstone River, a major tributary of the Missouri.
Kamis, 25 Agustus 2011
Powder River Basin
On my recent journey through Nebraska and eastern Wyoming, I was amazed at the number of coal trains that were streaming eastward; each more than a mile long, the trains were spaced by no more than a few miles. Originating at surface mines in the vicinity of Gillette, Wyoming, this caravan delivers a million tons of coal per day to power plants across the central and eastern U.S.
The Powder River Basin is defined by both its geography and its geology. Covering most of northeast Wyoming and part of southeast Montana, the basin stretches between the Bighorn Mountains of north-central Wyoming and the Black Hills of western South Dakota. Its southern border is the topographic divide between the North Platte watershed, to the south, and the watersheds of the Powder and Cheyenne Rivers to the north; more northern parts of the basin are also drained by the Tongue and Little Missouri Rivers. Geologically, the Powder River Basin is a broad bowl of Precambrian basement rock that gradually filled with sediments from the Paleozoic, Mesozoic and Cenozoic Eras; Cretaceous sandstones and shales, deposited by an inland seaway, form the thickest layer of sediments and lie just beneath Paleocene coal, the remnant of vast swamps and peat bogs that covered this region 60 million years ago. Compressed by younger Tertiary sediments, the plant debris turned to coal, since brought near the surface by the Miocene Uplift and subsequent erosion.
Powder River Basin coal, desired for its low sulfur and ash content, provides 40% of the coal used in the United States. Unfortunately (for coal advocates), much of this coal, buried under thick layers of Tertiary rock, is not economically accessible; nevertheless, seams near the surface should last for another 20 years or so and mining leases are still being granted by the U.S. government. While most Americans remain dependent on coal for their electric power, environmentalists continue to push for cleaner, renewable sources of energy; the Powder River Basin is, after all, the leading source of carbon-bearing fuel in our country.
The Powder River Basin is defined by both its geography and its geology. Covering most of northeast Wyoming and part of southeast Montana, the basin stretches between the Bighorn Mountains of north-central Wyoming and the Black Hills of western South Dakota. Its southern border is the topographic divide between the North Platte watershed, to the south, and the watersheds of the Powder and Cheyenne Rivers to the north; more northern parts of the basin are also drained by the Tongue and Little Missouri Rivers. Geologically, the Powder River Basin is a broad bowl of Precambrian basement rock that gradually filled with sediments from the Paleozoic, Mesozoic and Cenozoic Eras; Cretaceous sandstones and shales, deposited by an inland seaway, form the thickest layer of sediments and lie just beneath Paleocene coal, the remnant of vast swamps and peat bogs that covered this region 60 million years ago. Compressed by younger Tertiary sediments, the plant debris turned to coal, since brought near the surface by the Miocene Uplift and subsequent erosion.
Powder River Basin coal, desired for its low sulfur and ash content, provides 40% of the coal used in the United States. Unfortunately (for coal advocates), much of this coal, buried under thick layers of Tertiary rock, is not economically accessible; nevertheless, seams near the surface should last for another 20 years or so and mining leases are still being granted by the U.S. government. While most Americans remain dependent on coal for their electric power, environmentalists continue to push for cleaner, renewable sources of energy; the Powder River Basin is, after all, the leading source of carbon-bearing fuel in our country.
Langganan:
Postingan (Atom)