1. Created By: Miss. Hoover

2.  Some of the changes happen so slowly that you would never see them.  For instance, it took about 6 million years for the Colorado River to carve the Grand Canyon.

3.  Earth’s surface is exposed to water, wind, ice, and growing plants. Each one of these can break down rocks into smaller pieces. This breaking down of rocks is called weathering.

4.  Some of the minerals in rocks dissolve in water. When this happens under ground, huge caverns can form.  Moving water that carries rough pieces of sand can also chip away rocks.

5.  Wind that contains sand wears away rock like sandpaper wears away wood.  If you imagine workers sandblasting a building, that is how wind can weather rocks.

6.  Liquid water collects in cracks in a rock. When the water freezes, it expands.  The expanding ice pushes apart the rock and breaks it.

7.  When you look at a side of a cliff, you might see a plant sprouting from a crack in the rock. This process loosens and breaks off bits of the rock.

8.  Erosion carries weathered materials away from a place. Deposition drops the materials in a new place.  Erosion and deposition destroy old landforms and create new ones. Moving water, wind, and moving ice cause erosion and deposition.

9.  Rain, streams, and rivers cause erosion. When the water moves across the land it will carry away soil, sand, and small rocks.  When the water slows down, the materials all out and are deposited.

10.  Wind can move and deposit particles of rock, soil, and sand.  Wind makes the most changes when it blows open areas such as deserts, plowed fields, and beaches.

11.  Glacier is a large body of moving ice. Glaciers that form in mountain valleys move downward very slowly. As they move, they scrape away pebbles, rocks, and huge boulders.  If a glacier melts and shrinks, the materials are deposited. At this front end and its sides, the glacier leaves behind a ridge of rocks called a moraine.

12.  Over millions of years, forces in Earth’s crust pushed up these mountains in two different ways.  Folded mountains are produced when land is squeezed together. There is a push on the land and it forces it upwards.  Fault-block mountains are produced when blocks of rock slide upward or downward along a fault. A fault is a crack in Earth’s crust. Land moves along in one of three ways.

13.  Normal fault: a block of land drops downwards. This process can form valleys with steep hills.  Reverse fault: a block of land is pushed upward. This is how California’s Sierra Nevada Mountains were formed.  Strike-slip fault: blocks of rock move sideways past each other. The San Andreas Fault in California is a this kind of fault.

14.  The Earth’s crust is broken into sections and they are called plates. The plates are always moving, although they move very slowly.

15.  Rapid changes occur quickly on the Earth’s surface. These are volcanoes, earthquakes, tsunamis, landslides, and floods.

16.  Melted rock below Earth’s surface is called Magma. When the magma heats and expands, it pushes in all directions. It moves to the Earth’s crust. An eruption will happen and throw hot boulders, ashes, gases, and cinders in into the air.  When the magma and gases build up and are trapped inside the mountain for a while, the pressure is enormous. It becomes so great, there is an explosion.

17.  An Earthquake happens when huge slabs of rock move against each other deep below Earth’s surface. The slabs will touch a fault.  The slabs stick together until the forces are pushing and the force is so great. Then the slabs will move a short distance. This jolt produces waves in the crust like ripples in a pond. The waves can be felt as an earthquake.

18.  A tsunamis is a giant ocean wave caused by an undersea earthquake. When the earthquake occurs on the ocean floor, it releases a lot of energy. The energy travels though the water and produces a small wave on the surface.  Finally, the wave will move outward in all directions.

19.  The force of gravity can cause rapid changes in the land.  The force of gravity pulling on rocks, soil, and mud downward creates a landslide.  Landslides will destroy structures such as hills and cliffs. But the new land is built up at the bottom of the landslide.

20.  Floods will sweep land away from one place and deposit it in another place.  River floods are usually caused by long, steady, heavy rains or a large amount of melting snow.