Chapter 8: Lesson 1 Notes

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1 Chapter 8: Lesson 1 Notes Mineral- a nonliving, naturally occurring solid that has its own regular arrangement of particles in it. Minerals are found in rocks and soil. There are more than 4,000 types of minerals. There are many uses for minerals, such as jewelry, pencils, and seasoning for food. Properties of Minerals Properties that scientists use to identify minerals are hardness, luster, color, streak, shape, and magnetism. Some minerals may smell sweet, sour, earthy, or like rotten eggs. Hardness Scientists test a mineral's hardness by how easily it can be scratched. They use a special chart called the Mohs scale. A mineral with a greater number can scratch minerals with lesser number. Ex: if a piece of topaz (8) is rubbed against a piece of quartz (7), the topaz will scratch the quartz. Luster Describes how a mineral's surface reflects light. A glassy luster is shiny, like glass. An earthy luster is chalky and dull. A metallic luster can look like polished metal and a soft shine has a waxy, silky, or pearly luster. Color Elements that make up a mineral make affect its color. The element copper gives malachite a green color. The mineral beryl is green from the element chromium.

2 Amethyst quartz gets its purple color from iron. Streak The color of a mineral in powdered form. To see a mineral's streak, you rub it on a hard, rough, white surface. This produces a fine powder. The powder can be the same as or very different from the mineral's outside appearance. Shape The shape of a mineral is not always easy to see. Some minerals have a definite shape. Mineral crystals are often in the shape of familiar solid figures. Magnetism A few minerals have magnetic properties. They can attract other metals. Pyrrhotite and magnetite are strongly magnetic.

3 Chapter 8: Lesson 2 What are rocks? Kinds of rocks: There are three kinds of rocks igneous, sedimentary, and metamorphic By looking at the minerals in the rocks, it is often possible to determine how the rock was formed. Igneous Rocks Igneous rocks are formed when melted rock cools and hardens. These rocks can form deep inside Earth or from lava that hardens on Earth s surface. As hot, liquid rock cools, crystals of minerals form. o Melted rock that cools slowly= large crystals o Melted rock that cools quickly=small crystals Granite=magma that cools slowly underground Basalt=lava that cools quickly Pumice=lava that is quickly cooled by air at the surface and has tiny holes where gases were trapped Sedimentary Rocks Sedimentary rocks from when layers of materials and rock particles settle on top of each other Minerals from water act like cement. Sandstone o Layers of sand are buried and put under pressure

4 Conglomerate o Large, rounded particles have been pressed together Metamorphic Rocks When solid rocks are squeezed and heated to high temperatures, the particles can take on many different arrangements. Metamorphic rocks are formed inside Earth from other rocks under heat and pressure. The Rock Cycle Rocks are constantly being formed and destroyed in a process called the rock cycle. Rocks may be changed from one kind to another in any order or stay the same for millions of years. Remains of organisms can be part of the rock cycle. Draw the rock cycle in your notebook. You can find the rock cycle on page 313 of your book. Identifying Rocks Scientists identify rocks by looking at how they formed. Scientists also consider mineral content, color, and texture. Minerals, color and texture in rock Rocks are made of mixtures of minerals and other materials Some rocks have many minerals; other rocks have one mineral Color helps scientists identify types of minerals in rocks. A rock s texture is the look and feel of the surface. Most rocks are made up of particles or other rocks called grains

5 Lesson 3: What makes up soil? Soil Formation Soil- a mixture of nonliving materials and decayed materials from organisms Many animals make their homes in soil, such as chipmunks and earthworms Soil takes many years to form Weathering- the slow process that breaks rocks into smaller pieces called sediment Causes of weathering- freezing and melting water, plant roots, chemicals in rain and snow Parts of Soil Organic matter- living materials and materials that were once alive o Living material contains tiny organisms such as bacteria, fungi worms and insects. o Break down plant and animal remains into substances that plants use as food. Humus- decaying matter o Dark brown color o Makes spaces in soil for air and water o Contains nutrients that plants need to grow Inorganic Matter- all nonliving materials in soil o Water, air and pieces of rock and minerals o Small spaces in soil hold water and air Layers of Soil o Over time, layers develop o Three basic layers Topsoil top layer of soil crumbly and brown mostly made of humus

6 most organic matter Subsoil Second layer of soil Different color than topsoil Contains minerals and small rocks Less organic matter than topsoil Bedrock Mostly solid rock Deeper in some places than others Water may seep into cracks and weather the bedrock May eventually become sediments in soil Kinds of Soil The size of sediments in soil determine the texture and ability to hold water Color of soil depends on what materials are in the soil o Clay- smooth with fine, tightly packed rock particles Can hold a lot of water May be different colors (clay with iron particles looks red) o Silt- slightly larger particles than clay particles Feels slipper but not sticky when wet o Sand- larger particles than clay and silt Water passes quickly through sand Sandy soil contains particles from different materials Common mineral in sand is quartz The color depends on what minerals is it (sand that forms from volcanic rock can be black Factors That Affect Soil Climate and type of rock affect how soil forms Temperature in weather can affect how fast or slow soil forms

7 Chapter 8: Lessons 4 and 5 Lesson 4: What are erosion and deposition? Erosion and Deposition Water, wind, and ice can carry particles from one place to another Erosion- the movement of materials away from a place Gravity = main force causing erosion (ex. Landslide- gravity quickly pulls rocks and soil downhill) Deposition- the process of laying down materials, such as rocks and soil Sediments can be deposited in different places by wind or water Water Erosion and Deposition Moving water causes erosion that shapes Earth s surface Rivers, rain waves, ocean currents and glaciers are all forms of moving water o Rivers- gravity causes rivers to flow As rivers flow downhill, they pick up and carry sediments such as rock, soil and sand Sediments erode the riverbeds by grinding against riverbeds again and again The faster a river flows, the more sediments it can carry and the heavier the sediments could be Fast-flowing river can form a V-shaped valley, slow rivers form looping bends Deltas- deposited material from the river o Rain- loosen sediments from the soil and carry them away Rain can cause flooding in low, flat areas Flooding damages soil, roads and buildings and can erode tons of soil and deposit it downhill To prevent soil erosion, farmers plow furrows perpendicular to the field s slope o Waves- cause erosion along coastlines Waves hit along rocks, which causes them to break

8 Sand and gravel in waves act like sandpaper and weather the rocks Waves can drop sand somewhere else to form other beaches; Storms, tides and currents erode beaches Grasses/plants help hold soil in place o Glaciers- water frozen in glaciers can cause erosion Gravity pulls glaciers along a valley and the glaciers grind rocks into sediments Over a long period of time, the valley becomes U-shaped Wind Erosion and Deposition Wind erosion, caused by dust, soil or sand blowing, changes sand dunes and fields o Sand dunes- large, loose deposits of sand The size and shape of a dune depends on: speed and direction, amount of sand available, and number of plants that live around the area o Fields- bare, plowed fields can become very dry due to wind Wind blows away topsoil, which takes a long time to replace Farmers often plant tall trees along the edges of fields Lesson 5: How does Earth s surface change? Earth s Plates Lithosphere- the solid, rocky outer-most layer of Earth o The lithosphere covers all of the Earth but it is not a solid sheet of material Plate- a section of the lithosphere o Broken into several large sections and many smaller ones o Several plates are larger than continents o Plate may contain continents, parts of the ocean floor, or both o Plates might move into each other, pull apart or grind past each other

9 Changes over Time Plate movements are small; some plates move less than one centimeter per year No matter how small, these movements can cause big changes to Earth s surface- some changes occur in days or even minutes These changes include mountains being built and valleys being formed Mountains form, earthquakes occur and volcanoes erupt in certain places where plates meet o Plate boundaries- edges where Earth s plates meet Converging boundary- two plates move into each other Spreading plate boundary- plates pull apart from each other Sliding plate boundary- two plates move past each other in opposite directions Sometimes you can see a crack in the land, called a fault, where two plates meet Constructive and Destructive Forces Constructive forces- build new features on Earth s surface Destructive forces- wear away or tear down features Mountains and Valleys Constructive forces form new mountains and valleys Mountains form when Earth s crust folds, tilts and lift as plates collide Valleys form at spreading plate boundaries Volcanoes Most volcanoes are located near converging plate boundaries As one plate moves into another plate, rock partially melts into magma Magma hot, liquid material inside Earth Eruption- when magma is forced to the surface through a weak spot in the lithosphere Lava- magma that reaches Earth s surface Gases such as water vapor and carbon dioxide are often mixed with lava

10 Volcanoes can form on continents and the ocean floor Hawaii is a string of volcanic islands Earthquakes Faults- cracks in the Earth s lithosphere where surrounding rocks have shifted and can occur anywhere Earthquakes most often occur at faults along plate boundaries Energy released in an earthquake can destroy things quickly o Landslides- downhill movements of large amounts of rock o Tsunamis- caused by underwater earthquakes; large waves of water that can crash into a coastline, wash away soil and destroy things