Look up the \"Channeled Scablands\" of eastern Washington. We see river landform
ID: 299462 • Letter: L
Question
Look up the "Channeled Scablands" of eastern Washington. We see river landforms on massive scales. For example, ripple marks which are normally a few centimeters high are several meters high. How could a river create river formations on a such a large scale?
Question 21 options:
-A large river carved these features over thousands of years of high flow.
-A north-flowing river was blocked by ice forming an ice dam. The ice dam broke flooding the landscape.-
-A large glacier was halted by a mountain as it was moving forward. Water built up along the base of the glacier causing high water pressure. The glacier rose slightly due to underlying water pressure. Water rushed out catastrophically flooding the landscape.
-A major ice dam broke and Glacial Lake Missoula flooded the landscape in short period of time.
-A large river carved these features over thousands of years of high flow.
-A north-flowing river was blocked by ice forming an ice dam. The ice dam broke flooding the landscape.-
-A large glacier was halted by a mountain as it was moving forward. Water built up along the base of the glacier causing high water pressure. The glacier rose slightly due to underlying water pressure. Water rushed out catastrophically flooding the landscape.
-A major ice dam broke and Glacial Lake Missoula flooded the landscape in short period of time.
Explanation / Answer
Answer- A north-flowing river was blocked by ice forming an ice dam. The ice dam broke flooding the landscape.
Channeled Scablands of eastern Washington in U.S. are described as a relatively barren and soil-free region which have dry flood channels, flat-lying basalt flows, coulees, dry falls, gravel fans and bars, giant current ripples etc. This phenomena was happened during Pleistocene epoch. Now, how these large features like giant current ripples or large potholes were formed? A huge amount of water is required to form such a ripple marks of this magnitude.
Scientists have discovered that the Clark Fork river valley which was blocked by southward progressing Cordilleran ice sheet and as a result of this incident a giant ice-lake is formed named as Missoula. This also had form a 2,000 feet high ice dam. Behind this dam, water of Clark Fork river was started to accumulate. Then this ice dam broke and a huge amount of water had shattered the ground and as a result of this giant ripples, gravel bars were formed.
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