When does flowing
water deposit the
sediments it is
carrying?
4.
Why does flowing
water deposit the
largest particles first?
3.
How does the speed of
flowing water affect
its ability to erode?
2.
What are two ways
that flowing water can
cause erosion?
1.
Use the following discussion cards for “How Flowing Water Causes Erosion” passage. I {Heart} Recess © 2014
Erosion by Glaciers!
Like flowing water, flowing ice erodes the land and deposits the material
elsewhere. Glaciers cause erosion in two main ways: plucking and abrasion.
Plucking is the process in which rocks and other sediments are picked up by a
glacier. The sediments freeze to the bottom of the glacier and are carried away
by the flowing ice. Abrasion is the process in which a glacier scrapes underlying
rock. The sediments and rocks frozen in the ice at the bottom and sides of a
glacier act like sandpaper. They wear away rock as the glacier flows over it.
They may also leave scratches and grooves in rock that show the direction the
glacier moved.
Valley glaciers form several unique features through erosion. As a valley
glacier flows through a V-shaped river valley, it scrapes away the sides of the
valley. It carves a U-shaped valley with nearly vertical walls. A line on the valley
walls, called the trim line, shows the highest level the glacier reached. A cirque is
a rounded hollow carved in the side of a mountain by a glacier. The highest cliff of
a cirque is called the headwall. An arête is a jagged ridge that remains when
cirques form on opposite sides of a mountain. A low spot in an arête is called a col.
A horn is a sharp peak that is left behind when glaciers erode all sides of a
mountain.
How Flowing Water Causes Erosion and Deposition!
Flowing water is a very important agent of erosion. It can erode both rock
and soil. Flowing water dissolves and carries away minerals in rock. This process
occurs both on the surface and under the ground. The process happens very
slowly. However, over millions of years, flowing water can dissolve massive
amounts of rock. Moving water also physically picks up and carries particles of
soil and rock. More rapidly flowing water has more energy, so it can carry larger
particles and a greater quantity of particles. What causes water to move more
quickly? The slope of the land over which the water flows is one factor. The
steeper the slope, the more rapidly the water flows. Another factor is the amount
of water that’s in a stream or river. With more water in the channel, moving
water flows more quickly.
Flowing water eventually slows down and deposits the sediments it is
carrying. It may slow down when it reaches flatter land. Or it may slow down
when it flows into a large body of still water, such as a lake or the ocean. A river
can also slow down if it overflows its banks and floods its floodplain. As soon as
flowing water starts to slow down, it starts dropping particles. It drops the
largest particles first and the smallest particles last I {Heart} Recess © 2014