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Section 12.1 Summary: Soil is the Living Component of Earth’s Crust (pages 406-421)
1) ______________________ is the mechanical and/or chemical breakdown of rock. It affects
rocks, caves, mountains, buildings and streets.
2) During ______________________ weathering, rocks are simply broken into smaller pieces.
The overall chemical makeup of the rock stays the same, so the smaller pieces are still similar
to the original rock. There are three common causes:
-_____________________________ is the most common type of mechanical
weathering. _________________ enters a crack in a rock, and when it freezes it expands. The
crack enlarges and the rock breaks apart.
-___________________ can also wedge their way into a crack in a rock. The rock is
pushed apart until it eventually crumbles and breaks.
-____________________ (such as earthworms, rodents, and ants) can also cause
weathering. As the animals move through the soil, they loosen sediments and push the surface,
leaving it vulnerable to other weathering processes.
3) In ___________________________, chemical reactions occur with rocks to create new
substances. The larger the ________________________ of rock, the faster the rate of chemical
weathering. Softer rocks may be dissolved and harder rocks may be weakened. Some common
causes:
-_____________________________ can dissolve minerals such as calcite, causing
caves.
-_____________________________ reacts with some rocks causing it to dissolve and
be washed away.
-The _________________________ of some organisms that live on rocks (such as
________________) can cause chemical weathering.
4) ______________________ is the process that loosens and moves weathered rock particles
(sediment) over Earth’s surface.
5) ______________________________ is the most powerful agent of erosion. The faster the
water flows, the bigger and denser are the sediments it can carry.
6) Meteorological processes, such as ___________ and _____________ can cause erosion.
Heavy rain can disturb the stability of a slope, causing ___________________. Wind can pick
up fine particles which act like ____________________ on Earth’s surface.
7) Geological processes, such as __________________ and __________________, can also
cause erosion. Weathering breaks down rock on mountainsides and hillsides. The force of
gravity pulls the rock and sediment down from higher places to lower places. _______________
flow across Earth’s surface, carving and scraping, pushing loose rocks and soil out of their path,
and dragging rocks and sediment far away.
8) All agents of erosion deposit the sediment they are carrying when
____________________________________________. _________________________ is the
final stage of erosion and is considered a constructive process because land features are
produced and built up.
9) _______________________ are an in-between stage in the rock cycle. Eventually
(thousands of years) these eroded materials will be recycled to form new rocks.
10) __________________ is a combination of eroded rocks and minerals, water, air, and
organic matter such as decaying plant and animal materials.