Earth’s Interior, Plate Tectonics

and Topographical

Maps

Haiti Earthquake 2010

Photos from CBS News & Boston.com

Why does it happen?

Earth’s Interior

1. How do we know that the Earth is made of layers?

Earth’s InteriorBy studying things such as

seismic waves sent out by earthquakes, scientists have found Earth is made of several layers including the crust, mantle, and core.

Earth’s Interior

2. What happens when earthquakes occur?

Earth’s InteriorWhen earthquakes occur,

vibrations are sent out through the Earth. The vibrations are called seismic waves.

Earth’s Interior

3. What is a tsunami?

Earth’s InteriorIf an earthquake

happens underwater, it can cause destructive water waves called tsunamis.

Earth’s Interior

4. Where can seismic waves travel?

Earth’s InteriorSeismic waves can

travel along the surface or through the Earth’s interior.

Earth’s Interior

5. Tell about the core of the Earth.

Earth’s Interior The core is the central part of

the planet. It is made of hot, dense metals that sank after Earth formed.

Iron and nickel are the two main elements that make up the core.

Earth’s Interior

6. What is the difference between the inner and outer core?

Earth’s Interior In the inner core, the

pressure is so great the iron and nickel cannot melt so they remain in a solid state. In the outer core, the metals are in a liquid state.

Earth’s Interior

7. Tell about the mantle.

Earth’s Interior The mantle surrounds the core

and is made of silicon, oxygen, iron, and magnesium. About 80% of the Earth’s volume is in the mantle. It is a solid that is able to flow and this property is called plasticity.

Earth’s Interior

8. What is the crust?

Earth’s InteriorThe crust is the thin,

outermost layer that covers the planet and floats on the plastic mantle.

Earth’s Interior

9. What are the two types of crust?

Earth’s Interior The continental crust is made

mostly of igneous rock called granite and makes up the continents. Beneath the oceans is the oceanic crust made of dense rock called basalt.

Basalt Rock Columns

Earth’s Interior

10. What is the thickness of each layer?

Earth’s Interior Crust = 32 km (continental) to 8 km

(oceanic)

Mantle = 2900 km

Outer core = 2250 km

Inner core = 1300 km

Plasticity

What is plasticity?

Plasticity 1 : the quality or state of being

plastic; especially: capacity for being molded or altered.

Occurs in the Mantle layer of the Earth’s Interior

Responsible for the movement and shape of the Earth’s plates.

Plate Tectonics1. Was the Earth always as we see it now?

Plate Tectonics The development of reasonably

accurate world maps, birthed the idea that the continents fit together like a jigsaw puzzle.

However, it wasn’t till Alfred Wegner, a German geophysicist and meteorologist, published his radical hypothesis of continental drift that the idea gain significance.

Alfred Wegner

Continental DriftWegner hypothesized that a

supercontinent called Pangaea had once existed, and that, during the Mesozoic period, this supercontinent began to fragment and drift apart.

2. Why was Wegner’s theory not widely

accepted?

Earth scientist argued that the coastlines of continents are constantly being changed by erosion and deposition, and that a fit today would be unlikely.

3. Would Wegner’s theory of continental

drift hold up?

Scientist surmised that a better fit would probably be the seaward edge of the continental shelves.

In the 1960s, Sir Edward Bullard and two associates produced a map of the continental shelves and fit them together. The result was an amazing fit!

Pangaea

4. Besides fit, was there any other

evidence supporting the theory?

Fossil Evidence Mesosaurus- Wegner cited that the aquatic

reptile whose remains are only found in the black shale of the Permian age in South America and southern Africa was evidence of a connection.

Fossil Evidence Glossopteris- a fern whose fossils have

been found in Africa, Australia, India, and South America also supported the theory that the continents were once connected.

Other Organisms

Mountain Ranges The Appalachian

Mountains range along the eastern side of North America and disappear off the coast of Newfoundland. Also, mountain ranges of similar ages and structure are found in Greenland, the British Isles, and Scandinavia.

What are the three types of plate boundaries?

Three Plate Boundaries

1.Divergent boundary

2.Convergent boundary

3.Transform boundary

Divergent Boundary Divergent boundaries occur

when plates are pulled away from each other.

New crust is formed when this occurs.

When this occurs on land, a rift, will be created that can result in the land breaking apart.

Divergent Boundary

Convergent boundaries

Convergent boundaries occur where plate are push together or converge.

The more dense plate will slide under the less dense plate.

Crust is destroyed and recycled back into the earth’s interior.

Oceanic-Continental Convergence

When an oceanic plate pushes into and subducts under a continental plate, the overriding continental plate is lifted up and a mountain range is created.

Even though the oceanic plate as a whole sinks smoothly and continuously into the subduction trench, the deepest part of the subducting plate breaks into smaller pieces.

These smaller pieces become locked in place for long periods of time before moving suddenly and generating large earthquakes.

Oceanic-Continental

Oceanic-Oceanic Convergence

When two oceanic plates converge one is usually subducted under the other and in the process a deep oceanic trench is formed.

Oceanic-oceanic plate convergence also results in the formation of undersea volcanoes.

Over millions of years, however, the erupted lava and volcanic debris pile up on the ocean floor until a submarine volcano rises above sea level to form an island volcano.

Oceanic-Oceanic

Continental-Continental Convergence

When two continents meet head-on, neither is subducted because the continental rocks are relatively light and, like two colliding icebergs, resist downward motion.

Instead, the crust tends to buckle and be pushed upward or sideways.

Continental-Continental

Transform-fault Boundaries

Transform-Fault Boundaries are where two plates are sliding horizontally past one another. These are also known as transform boundaries or more commonly as faults.

Most transform faults are found on the ocean floor. They commonly offset active spreading ridges, producing zig-zag plate margins, and are generally defined by shallow earthquakes.

Transform-fault Boundaries

The San Andreas fault zone in California is a transform fault that connects the East Pacific Rise, a divergent boundary to the south, with the South Gorda -- Juan de Fuca -- Explorer Ridge, another divergent boundary to the north.

Transform-fault

Last fifteen slides fromhttp://www.platetectonics.com/book/page_5.a

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Topographic Maps

Lesson Objectives Define a topographic map and state its uses. Describe how contour lines show the elevations, shape, and slope of the land. Identify the meanings of some symbols and colors used on topographic maps.

What is a topographic map?

A topographic map, also known as a contour map, is a map that shows the shape of the land using contour line. It is a map that shows an elevation field, meaning how high and low the ground is in relation to sea level.

What are contour lines?

Contour lines are lines that connect points that are of the same elevation.

They show the exact elevation, the shape of the land, and the steepness of the land’s slope.

Contour lines never touch or cross.

Other Topographic TermsMap scale – compares distances on

the map with distances on earth.

Legend – explains symbols used on the map.

Index contours – contour lines that are labeled to help you find the contour interval.

What is a contour interval?

A contour interval is the difference in elevation between two contour lines that are side by side.

Remember that a contour interval is not the distance between the two lines – to get the distance you need to use the map scale.

?20

720

740

760

780

What if my contour lines are close

together?

If the contour lines are close together, then that indicates that the area has a steep slope.

What if my contour lines are far apart?

If the contour lines are far apart, then that indicates the land has a gentle slope (low slope).

What do the dark colored contour lines mean?

The dark colored contour lines represent every fifth contour line to make it easier to read the map.

More on Contour Lines

Contour lines form V’s that point upstream when they cross a stream.

It is important to remember that they point in the opposite direction as the flow of water.

Now that I know what a topographic map is, how do I read it?

First determine the contour interval (the distance between each contour line)

Then determine the map scale (usually at the bottom of the map)

Identify any hills or depressions

Use the legend to identify man made features.

Continued:Look for areas where the contour lines are close together – they indicate a steep area.

Look for areas where the contour lines are spread apart – they indicate a gentle slope.

Review Questions1.How are contour lines drawn on

maps?2.How does a contour map show

whether a slope is gentle or steep?

3.How is distance measured on a contour map?

4.What does contour intervals tell us?

5.Why are topographic maps important?