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8th Grade Science Unit 8: Changes Over Time

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Presentation on theme: "8th Grade Science Unit 8: Changes Over Time"— Presentation transcript:

1 8th Grade Science Unit 8: Changes Over Time
Lesson 2: Changes in the Rocks Vocabulary of Instruction

2 1. Landform Landforms are natural features of the landscape.
They are natural physical features of the earth's surface. Examples of Landforms are: valleys, plateaus, mountains, plains, hills, loess, and glaciers.

3 1-A. Landform - Valley A valley is a hollow or surface depression of the earth surrounded by hills or mountains. It is a natural trough in the earth's surface, that slopes down to a stream, lake, or the ocean, formed by water and/or ice erosion.

4 1-B. Landform - Plateau A plateau is a large highland area of fairly level land separated from surrounding land by steep slopes. Some plateaus, like the plateau of Tibet, lie between mountain ranges. Others are higher than surrounding land. Plateaus are widespread, and together with enclosed basins they cover about 45 percent of the Earth's land surface.

5 1-C. Landform - Mountains
Mountains are formed by volcanism, erosion, and disturbances or uplift in the earth's crust. Most geologists believe that the majority of mountains are formed by geological forces such as heat and pressure producing changes and movements under the earth's crust.

6 1-D. Landform - Plains Plains are broad, nearly level stretches of land that have no great changes in elevation. Plains are generally lower than the land around them; they may be found along a coast or inland. Coastal plains generally rise from sea level until they meet higher landforms such as mountains or plateaus. Inland plains may be found at high altitudes.

7 1-E. Landform - Hills Hills are elevations of the earth's surface that have distinct summits, but are lower in elevation than mountains. Hills may be formed by a buildup of rock debris or sand deposited by glaciers and wind. Hills may be created by faults. Faults are a slight crack in the earth which can cause earthquakes. Hills are formed when these faults go slightly upward.

8 1-F. Landform - Loess Loess is a geologically recent deposit of silt or material which is usually yellowish or brown in color and consisting of tiny mineral particles brought by wind to the places where they now lie. It is a product of past glacial activity in an area. It is a sedimentary deposit of mineral particles which are finer than sand but coarser than dust or clay, deposited by the wind. Loess is a type of silt which forms fertile topsoil in some parts of the world. Loess deposits are usually a few meters thick.

9 1-G. Landform - Glacier A glacier is a huge mass of ice that flows slowly over land. They form in the cold polar regions and in high mountains. The low temperatures in these places enable large amounts of snow to build up and turn into ice. Most glaciers range in thickness from about 91 to 3,000 meters. Glaciers are formed when more snow falls during the winter than melts and evaporates in summer.

10 2. Contour Line (Isoline)
A contour line is a line on a map that connects points or places of equal elevation. The bottom part of the diagram shows some contour lines with a straight line running through the location of the maximum value. The curve at the top represents the values along that straight line.

11 3. Topographic Map (Contour Map)
Is a map that shows the change in elevation of the Earth’s surface using contour lines. It shows shapes and features of the Earth surface such as roads, lakes, and cities. Traditional definitions require a topographic map to show both natural and man-made features.

12 4. Rock Cycle The Rock cycle describes the dynamic transitions through geologic time among the three main rock types: sedimentary, metamorphic, and igneous. As the diagram to the right illustrates, each type of rock is altered, changed, or destroyed when it is subject to factors such as heat, pressure, cooling, and erosion.

13 4-A. Rock Cycle - Diagram The rock cycle starts at is the magma chamber. The magma comes out of the volcano and cools into igneous rocks. Next, the igneous rocks erode and turn into sediments. The sediments go through years of pressure and cementation which turns the sediments into sedimentary rock layers. Once again the sedimentary rocks go through heat and pressure and turn into metamorphic rocks. Then the new metamorphic rocks go through heat and turn into magma.

14 4-B. Rock Cycle – Diagram … Cont…
Also, igneous rocks can go through heat and pressure and become metamorphic rocks. Metamorphic and sedimentary rocks can become sediments. That is how the rock cycle works.

15 4-C. Rock Cycle – Diagram Cont…
Another representation of the rock cycle processes is shown on the picture to the left.

16 4-D. Rock Cycle Three Types of Rocks
1. Igneous Rock Lava flowing from a volcano in Hawaii forms igneous rocks.

17 4-D. Rock Cycle Three Types of Rocks
2. Metamorphic rock In Arizona metamorphic rocks show formerly flat sedimentary layers squeezed into new shapes.

18 4-D. Rock Cycle Three Types of Rocks
3. Sedimentary Rock. Metamorphic Rocks in Hawaii have been broken into sediments and have accumulated on this beach, where they might form a sedimentary rock through pressure and cementation.

19 4-D. Rock Cycle Three Types of Rocks
Sedimentary and metamorphic rocks in Arizona were broken into sediments and carried away, leaving the Grand Canyon behind, one of the wonders of the world.


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