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The Rock Cycle
Rocks are constantly changing in a process called the rock cycle
most of the changes occur naturally
Weathering (1 main pt.)
Sediment comes from larger rocks that have broken down or worn away by a natural process
called weathering
Mechanical Weathering (6 main pts. and 1ex.)
Mechanical weathering is the physical breakup or disintegration of rocks.
Climate change can also cause mechanical weathering.
During the freeze-thaw period, snow and ice melt in the daytime allowing water to seep into
cracks in rock. At night the temperature falls below 0C and the water freezes and expands,
pushing the cracks wider apart. Finally the rock breaks apart. this process is called frost
wedging.
Mechanical Weathering cont.
Another type of mechanical weathering occurs when wind and water away the surfaces of rocks
(erosion) and carry the pieces to another place, where the pieces build up (deposition).

Ex. (1) Dust storms and (2) muddy silt along a river bed.
Erosion occurs more easily when small pieces of grit that are suspended in the wind and water
act like sandpaper on Earth's surface.
During the Ice Age glaciers (large bodies of ice) flowed across Earth's surface carving and
scraping and lifting away rock and soil.the glaciers carried the sediment far away.
Chemical Weathering (2 main pts. & 1 ex)
Chemical reactions can speed up the process of erosion.
Chemical weathering involves the breakdown or decomposition of minerals as a result of a
chemical reaction with (1) water, with (2) other chemicals dissolved in water or with (3) gases in
the air.
Ex. Acid rain (containing chemicals from air pollution reacting with rocks)
Biological Weathering (3 main pts & 2 ex.s)
Biological weathering is the physical or chemical breakdown of rock caused by living
organisms, such as plants, animals, bacteria and fungi.
Ex. when a plant root wedges into a rock by forcing its way into a crack.
Chemical reactions can also take place between rock material and acidic fluids that are
produced by plant roots, bacteria, fungi and some small insects and small animals.
If the physical environment changes, the rocks will also change
Ex. natural processes such as earthquakes, volcanic eruptions and weathering have an impact on
the rock cycle.