As ancient glaciers flowed over basalt at Devil’s Postpile National Monument (California), rock and sediment in the ice left scratches on the bedrock. These scratches, “ striations ,” can be used to understand past ice flow.
What are glacial scars?
Glacial striations are a series of long, straight, parallel lines or grooves scratched onto a bedrock surface by rock fragments lodged in the base of a moving glacier . They typically form on hard rock, such as quartzite, that is relatively resistant to erosion.
What are the parallel scratches in rock called?
(Plural: striae) Also called striation Geology any of the parallel scratches or grooves on the surface of a rock caused by abrasion resulting from the passage of a glacier, motion on a fault surface, etc.
What do we call the long scratches that are etched into rocks as glaciers move over top of them?
Glacial striations are long scratches that form in the direction of glacial movement. ... Glacial erosion can also create a roche moutonnee, which is a mass of rocks carved by a passing glacier.
Which term means scratches in rocks caused by glaciers?
Glacial grooves and striations are gouged or scratched into bedrock as the glacier moves downstream. Boulders and coarse gravel get trapped under the glacial ice, and abrade the land as the glacier pushes and pulls them along.
What are 3 main types of glacial erosion?
Glacial erosion involves the removal and transport of bedrock or sediment by three main processes: quarrying (also known as plucking), abrasion, and melt water erosion .
What does glacial erosion look like?
The movement of ice in the form of glaciers has transformed our mountainous land surfaces with its tremendous power of erosion. U-shaped valleys , hanging valleys, cirques, horns, and aretes are features sculpted by ice.
Why did no one believe Wegener’s theory?
The main reason that Wegener’s hypothesis was not accepted was because he suggested no mechanism for moving the continents . He thought the force of Earth’s spin was sufficient to cause continents to move, but geologists knew that rocks are too strong for this to be true.
What are glacial deposits called?
Debris in the glacial environment may be deposited directly by the ice (till) or, after reworking, by meltwater streams (outwash). The resulting deposits are termed glacial drift. The resulting deposit is called a flow-till by some authors. ...
What is glacial evidence?
The most apparent evidence is of course the glacial drift itself. ... Glacial drift refers to the rock material ground up and transported by a glacier and deposited by or from the ice (till) or in water derived from the melting of ice (outwash or lake sediment).
What is striated rock?
Striations are lines or scratches on rock surfaces , usually no more than a few millimeters in depth, produced by the process of glacial abrasion (Glasser and Bennett, 2004). From: Developments in Earth Surface Processes, 2015.
What is a large rock transported by a glacier called?
Glacial erratics are stones and rocks that were transported by a glacier, and then left behind after the glacier melted. Erratics can be carried for hundreds of kilometers, and can range in size from pebbles to large boulders. Scientists sometimes use erratics to help determine ancient glacier movement.
What are the rock layers?
There are three kinds of rock: igneous, sedimentary, and metamorphic .
What is the greatest agent of erosion?
Liquid water is the major agent of erosion on Earth. Rain, rivers, floods, lakes, and the ocean carry away bits of soil and sand and slowly wash away the sediment.
How do glaciers cut rock?
As a glacier flows downslope, it drags the rock, sediment, and debris in its basal ice over the bedrock beneath it, grinding it . This process is known as abrasion and produces scratches (striations) in bedrock surface.
What are glaciers What is the reason for their slow movement?
The sheer weight of a thick layer of ice, or the force of gravity on the ice mass , causes glaciers to flow very slowly. Ice is a soft material, in comparison to rock, and is much more easily deformed by this relentless pressure of its own weight.
