8

th

Grade Science

Unit 8: Changes Over Time Lesson 2: Changes in the Rocks Vocabulary of Instruction

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

.

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,

erosion formed by water and/or ice

.

1-B. Landform - Plateau

• A

plateau surface

. 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

1-C. Landform - Mountains

•

Mountains by volcanism, erosion, and disturbances or uplift in the earth's crust

. are

formed

• 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.

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.

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

.

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

forms . • Loess is a type of silt which

fertile topsoil

in some parts of the world. • Loess deposits are usually a

few meters thick

.

1-G. Landform - Glacier

• A

glacier of ice that flows slowly over land

• They form in the cold polar regions and in high mountains. • The is a .

huge mass 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.

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

.

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

.

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

.

4-A. Rock Cycle - Diagram

• The

rock cycle starts

at is the

magma chamber

cools into . The magma comes out of the volcano and

igneous rocks

.

• Next, the of

igneous rocks erode

and turn into

sediments

. • The sediments go through years

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

.

4-B. Rock Cycle – Diagram … Cont…

• Also,

igneous rocks

can go through

heat and pressure

become and

metamorphic rocks

.

•

Metamorphic and sedimentary rocks

can become

sediments

.

• That is how the rock cycle works.

4-C. Rock Cycle – Diagram Cont…

• Another representation of the

rock cycle processes

is shown on the picture to the left.

4-D. Rock Cycle Three Types of Rocks

1. Igneous Rock

• Lava flowing from a

volcano

in Hawaii

forms igneous rocks

.

4-D. Rock Cycle Three Types of Rocks

2. Metamorphic rock

• In Arizona metamorphic rocks show

formerly flat sedimentary layers

squeezed into new shapes.

4-D. Rock Cycle Three Types of Rocks

3. Sedimentary Rock.

• Metamorphic Rocks in Hawaii have been

broken into sediments accumulated on this beach

and have , where they might

form a sedimentary rock

through pressure and cementation.

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

.