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Question

How were each of these mountains formed?
1. Catskills:
2. Sierra nevadas:
3. Mauna Loa:
4. Rockies:
5. Black Hills:

Answer 1

The history of the Catskill Mountains is a geologic story come full circle, from erosion, deposition and uplift back to erosion. The Catskill Mountains are more of a dissected plateau than a series of mountain ranges. The sediments that make up the rocks in the Catskills were deposited when the ancient Acadian Mountains in the east were rising and subsequently eroding. The sediments traveled westward and formed a great delta into the sea that was in the area at that time.

The eastern escarpment of the Catskills is near the former edge of this delta, as the sediments deposited in the northeastern areas along the escarpment were deposited above sea level by moving rivers and the Acadian Mountains were located roughly where the Taconics are located today (though significantly larger). The further east you travel, the finer the sediment that was deposited and the thus the rocks change from gravel conglomerates to sandstones and shales. Even further east, these fresh water deposits intermingle with shallow marine sandstones and shales until the end in deeper water limestones.

The uplift and erosion of the Acadian Mountains was occurring during the Devonian and early Mississippian period (395 to 325 million years ago). Over that time, thousands of feet of these sediments built up, slowly moving the Devonian seashore further and further west.

By the middle of the Mississippian period, the uplift stopped and the Acadian Mountains had been eroded so much that sediments no longer flowed across the Catskill Delta.

Over time the sediments were buried by more sediments from other areas until the original Devonian and Mississippian sediments were deeply buried and slowly became solid rock. Then the entire area experienced uplift, which caused the sedimentary rocks to begin to erode. Today, those upper sedimentary rocks have been completed removed, allowing the Devonian and Mississippian rocks to be exposed. Today’s Catskills are a result of the continued erosion of these rocks, both by streams and in the recent past by glaciers.

In successive Ice Ages, both valley and continental glaciers have widened the valleys and the notches of the Catskills and rounded the mountains. Grooves and scratches in exposed bedrock provides evidence of the great sheets of ice that once traversed through the region. Even today the erosion of the mountains continue, with the region’s rivers and streams deepening and widening the mountains’ valleys and cloves.

Answer 2

http://www.wikipedia.org

Answer 3

(1) CATSKILLS

The history of the Catskill Mountains is a geologic story come full circle, from erosion, deposition and uplift back to erosion. The Catskill Mountains are more of a dissected plateau than a series of mountain ranges. The sediments that make up the rocks in the Catskills were deposited when the ancient Acadian Mountains in the east were rising and subsequently eroding. The sediments traveled westward and formed a great delta into the sea that was in the area at that time.

The eastern escarpment of the Catskills is near the former edge of this delta, as the sediments deposited in the northeastern areas along the escarpment were deposited above sea level by moving rivers and the Acadian Mountains were located roughly where the Taconics are located today (though significantly larger). The further east you travel, the finer the sediment that was deposited and the thus the rocks change from gravel conglomerates to sandstones and shales. Even further east, these fresh water deposits intermingle with shallow marine sandstones and shales until the end in deeper water limestones.

The uplift and erosion of the Acadian Mountains was occurring during the Devonian and early Mississippian period (395 to 325 million years ago). Over that time, thousands of feet of these sediments built up, slowly moving the Devonian seashore further and further west.

By the middle of the Mississippian period, the uplift stopped and the Acadian Mountains had been eroded so much that sediments no longer flowed across the Catskill Delta.

Over time the sediments were buried by more sediments from other areas until the original Devonian and Mississippian sediments were deeply buried and slowly became solid rock. Then the entire area experienced uplift, which caused the sedimentary rocks to begin to erode. Today, those upper sedimentary rocks have been completed removed, allowing the Devonian and Mississippian rocks to be exposed. Today’s Catskills are a result of the continued erosion of these rocks, both by streams and in the recent past by glaciers.

In successive Ice Ages, both valley and continental glaciers have widened the valleys and the notches of the Catskills and rounded the mountains. Grooves and scratches in exposed bedrock provides evidence of the great sheets of ice that once traversed through the region. Even today the erosion of the mountains continue, with the region’s rivers and streams deepening and widening the mountains’ valleys and cloves.


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(2) SIERRA NEVADAS

The geological history of the Sierra Nevada begins in the Jurassic period, approximately 150 million years ago. At that time, an island arc collided with the West coast of North America and raised a set of mountains, in an event called the Nevadan orogeny. This event produced metamorphic rock. At roughly the same time, a subduction zone started to form at the edge of the continent. This means that an oceanic plate started to dive beneath the North American plate. Magma from the melting oceanic plate rose and created plutons of solid granite, deep below the surface. These plutons formed at various times, from 115 million to 87 million years ago. By 65 million years ago, the proto-Sierra Nevada was worn down to a range of rolling low mountains, a few thousand feet high.

About 25 million years ago, the Sierra Nevada started to rise and tilt to the west. Rivers started cutting deep canyons on both sides of the range. The Earth's climate cooled, and ice ages started about 2.5 million years ago. Glaciers carved out characteristic U-shaped canyons throughout the Sierra. The combination of river and glacier erosion exposed the granitic plutons previously buried, leaving only a remnant of metamorphic rock on top of some Sierra peaks. The rocks of the ancient plutons are known as the Sierra Nevada batholith.

Uplift of the Sierra Nevada continues today, especially along its eastern side. This uplift causes large earthquakes, such as the Lone Pine earthquake of 1872.

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(3) MAUNA LOA

Mauna Loa is a shield volcano, meaning that its slopes are extremely shallow. This is because its lavas are extremely fluid. Eruptions are very rarely violent, and the most common form of activity involves lava fountains feeding lava flows. Typically, at the start of an eruption a rift up to several kilometres long opens up, with lava fountains occurring along its length in a so-called 'curtain of fire'. After a few days, activity normally becomes concentrated at one vent.

Mauna Loa from the Saddle RoadEruptions occur in three regions on the mountain: at the summit, and in two 'rift zones' extending northeast and southwest of the summit. About 40 per cent of eruptions in the last two hundred years have occurred at the summit, 30 per cent in the northeast rift zone and 25 per cent in the southwest rift zone. At the mountain's summit is a large caldera, measuring 3×5 km in diameter. The caldera probably formed 1,000-1,500 years ago when a very large eruption from the northeast rift zone emptied out the shallow magma chamber beneath the summit, which then collapsed.

Beneath the volcano, seismic data can reveal the location of the magma chambers which feed activity. Some types of seismic waves cannot travel through liquid rock, and so magma chambers cast 'shadows' in seismic data. This reveals a magma chamber about 3km beneath the summit, and smaller magma bodies beneath the rift zones.

Origins
Mauna Loa probably began erupting about 100,000 years ago, and has grown steadily since then. Like all of the Hawaiian islands, Mauna Loa has its origins in a hotspot - a plume of magma rising from deep in the Earth's mantle. The hotspot remains in a fixed position, while the pacific plate drifts over it at a rate of about 10 centimetres a year. The upwelling of the hot magma creates volcanoes, and each individual volcano erupts for a few million years before the movement of the plate carries it away from the rising magma.

The hotspot has existed for at least 80 million years, and a chain of old volcanoes stretches over 3,600 miles away from the hotspot. Currently, the hot spot feeds activity at five volcanoes - Mauna Loa, Kilauea, and Hualalai on the Big Island, Haleakala on Maui, and Loihi, a submarine volcano south of the Big Island and the youngest Hawaiian volcano. Mauna Loa is the largest of these six volcanoes, although currently Kilauea is the site of the most intense volcanic activity.

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(4) ROCKIES

The Rocky Mountains are commonly defined to stretch from the Liard River in British Columbia, down to the Rio Grande in New Mexico. The mountains can also be considered to run all the way to Alaska or Mexico, but usually those mountains are considered to be part of the entire American cordillera, rather than part of the Rockies.

The younger ranges of the Rocky Mountains uplifted during the late Cretaceous period (140 million-65 million years ago), although some portions of the southern mountains date from uplifts during the Precambrian (3,980 million-600 million years ago). The mountains' geology is a complex of igneous and metamorphic rock; younger sedimentary rock occurs along the margins of the southern Rocky Mountains, and volcanic rock from the Tertiary (65 million-1.8 million years ago) occurs in the San Juan Mountains and in other areas. Millennia of severe erosion in the Wyoming Basin transformed intermountain basins into a relatively flat terrain. The Tetons and other north-central ranges are magnificent granitic intrusions of folded and faulted rocks of Paleozoic and Mesozoic age (Peterson 1986; Knight 1994).

Periods of glaciation occurred from the Pleistocene Epoch (1.8 million-70,000 years ago) to the Holocene Epoch (fewer than 11,000 years ago). Recent episodes included the Bull Lake Glaciation that began about 150,000 years ago and the Pinedale Glaciation that probably remained at full glaciation until 15,000-20,000 years ago (Pierce 1979). Ninety percent of Yellowstone National Park was covered by ice during the Pinedale Glaciation (Knight 1994). The "little ice age" was a period of glacial advance that lasted a few centuries from about 1550 to 1860. For example, the Agassiz and Jackson glaciers in Glacier National Park reached their most forward positions about 1860 during the little ice age (Grove 1990).

Water in its many forms sculpted the present Rocky Mountain landscape (Athearn 1960). Runoff and snowmelt from the peaks feed Rocky Mountain rivers and lakes with the water supply for one-quarter of the United States. The rivers that flow from the Rocky Mountains eventually drain into three of the world's Oceans: the Atlantic Ocean, the Pacific Ocean, and the Arctic Ocean. These rivers include:

Mountains.Arkansas River
Athabasca River
Clark Fork River
Colorado River
Columbia River
Fraser River
Kootenay River
Missouri River
Peace River
Platte River
Rio Grande
Saskatchewan River
Snake River
Yellowstone River
The Continental Divide is located in the Rocky Mountains and designates the line at which waters flow either to the Atlantic or Pacific Oceans. Triple Divide Peak (8020 feet/2444 m) in Glacier National Park (US) is so named due to the fact that water which falls on the mountain reaches not only the Atlantic and Pacific, but the Arctic Ocean as well.

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(5) BLACK HILLS

The Black Hills are a small, isolated mountain range rising from the Great Plains of North America in western South Dakota and extending into Wyoming, USA. Set off from the main body of the Rocky Mountains, the region is somewhat of a geological anomaly. The region is considered sacred by many of the Plains Native Americans. It is accurately described as an "island of trees in a sea of grass." The Black Hills are home to the tallest peaks between the Rocky Mountains and the Alps in Europe (not counting undersea mountains).

The geology of the Black Hills is complex. A Tertiary mountain-building episode is responsible for the uplift and current topography of the Black Hills region. This uplift was marked by volcanic activity in the northern Black Hills. The southern Black Hills are characterized by Precambrian granite, pegmatite, and metamorphic rocks that comprise the core of the entire Black Hills uplift. This core is rimmed by Paleozoic, Mesozoic, and Cenozoic sedimentary rocks.