Science Lesson Ashley Smith

Earth Materials Earth materials are solid rocks and soils, water, and the gases of the atmosphere. The varied materials have different physical and chemical properties, which make them useful in different ways, for example, as building materials, (e.g., stone, clay, marble), as sources of fuel, (e.g., petroleum, natural gas) or for growing the plants we use as food. Earth materials provide many of the resources that humans use.

Rocks Rocks have different physical properties. Rocks are useful to human beings in many ways. Many rocks are composed of smaller parts called minerals. Rocks have some characteristics that can’t be seen, but can be “tested” for. Earth materials change over time, usually due to slow changes. Changes in rocks is called weathering, and it can be caused by wind, water, or anything that causes small pieces of rock to break off from larger rocks.

Rocks Continued There are three types of rocks---igneous, sedimentary, and metamorphic. Igneous rocks form from melted rock that has cooled and hardened. Sedimentary rocks form from layer of sediment. Metamorphic rocks have been changed by heat and pressure. The Earth is a ball of rock with three layers---crust, mantle, and core. (3-30 miles thick).

Soil Soils have properties of color and texture, capacity to retain water, and ability to support the growth of many kinds of plants, including those in our food supply. Soils are made up of smaller parts, including both minerals (from weathered rocks), and plant and animal remains. Soils also contain air and water. One variable property of soil is “water-holding capacity,” a property that is important for plant growth and some other functions of soil.

Soil Continued Soil is an important resource that can be harmed. There are several ways to conserve soil---strip cropping, contour plowing, no-till farming, and planting trees

Water Water is one of the most important substances on Earth. More than two-thirds of Earth’s surface is covered by water. All people need fresh water, but most of Earth’s water is not fresh. Most of the water on Earth is salt water. Estuaries are places where fresh water from a river mixes with salt water from the ocean. Water can exist in three different forms in nature---liquid (water), solid (ice), gas (water vapor). The water cycle is the movement of water from Earth’s surface into the air and back to the surface again.

The Water Cycle

Processes That Change the Earth’s Surface Earth’s surface has many types of landforms---mountains, valleys, canyons, plains, plateaus, and barrier islands. Weathering breaks down rocks in several ways. Erosion moves pieces of rock around in many ways. The movement of glaciers, wind, and water can change the land. Earthquakes and volcanoes cause rapid changes to the land.

Earthquakes An earthquake is a sudden, rapid shaking of the earth caused by a release of energy stored in rocks. Earthquakes are a natural phenomenon. They are happening all the time but are often not even noticed by people until they cause visible damage. We see the results of earthquakes in landslides, tsunamis, faults and rifts.

Volcanoes Volcanoes also can occur as a result of plate movement. A volcano is a vent in the surface of the Earth through which magma (molten rock called “lava” when it reaches the surface) and associated gases, erupt. Materials ejected from the vent could include: cinder—dark colored pieces of rock thrown from a volcano pumice—bubbly, frothy rock that is hardened ash—fine grained particles less than 2 mm across Volcanoes also trigger mudflows, avalanches, and cracks or fissures in the Earth’s surface.

Landslides A landslide is a mass of rocks, soil and debris that suddenly slides down a slope. A landslide can be caused by rocks breaking from an outcrop and tumbling down a cliff, heavy rains soaking the ground causing mud to flow down a hillside, or an earthquake shaking the ground causing it to move down a steep slope.

Atmospheric Gases The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth’s gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation. The atmosphere is…..78% Nitrogen, and 21% Oxygen. There are small amounts of argon, carbon dioxide and water vapor too.