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The Laurentide ice sheet (LIS) was a massive sheet of ice that covered millions of square miles, including most of Canada and a large portion of the Northern United States, multiple times during the Quaternary glaciation epochs, from 2.58 million years ago to the present.
These glaciers penetrated up to 50 kilometres (31 mi) into the lowlands. Even valleys that appear rather insignificant today such as those of the Isar , Loisach and Ammer rivers, were able to produce large tongues of ice when their glaciers were fed by larger ones, such as the Inn Valley Glacier (e.g. via the Fern Pass ).
Beneath the surface, great masses of molten rock were injected and hardened in place. [12] For 100 million years the effects of plate collisions were focused very near the edge of the North American plate boundary, far to the west of the Rocky Mountain region. It was not until 70 million years ago that these effects began to reach the Rockies. [12]
Initially, Arkansas bauxite met 90% of US aluminum demand. Underground mining before and during World War II gave way to open pit mining in the 1960s. During the war, up to six million tons were mined in 1943. Arkansas bauxite mines were often passed over in favor of higher quality bauxite reserves in the Caribbean and mining ceased in 1982.
A chronology of climatic events of importance for the Last Glacial Period, about the last 120,000 years The Last Glacial Period caused a much lower global sea level.. The Last Glacial Period (LGP), also known as the Last glacial cycle, occurred from the end of the Last Interglacial to the beginning of the Holocene, c. 115,000 – c. 11,700 years ago, and thus corresponds to most of the ...
During the Last Glacial Maximum, much of the world was cold, dry, and inhospitable, with frequent storms and a dust-laden atmosphere. The dustiness of the atmosphere is a prominent feature in ice cores; dust levels were as much as 20 to 25 times greater than they are in the present.
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A subglacial meltwater channel is a channel beneath an ice mass, such as ice sheets and valley glaciers, roughly parallel to the main ice flow direction.These meltwater channels can have different sizes, ranging from very small channels of a metre deep and wide to big valleys which can be up to a kilometre wide.