Earth Shakes, Rattles, and Rolls

Plate Tectonics Volcanoes

Earthquakes

What is the relationship between the earth’s plates, volcanoes, and earthquakes?

http://www.extremescience.com/PlateTectonicsmap.htm

Plates

Earthquakes

http://hsv.com/scitech/earthsci/quake.htm

Volcanoes

Let’s look at those maps again.

Plates

Earthquakes

Volcanoes

Earthquakes and Volcanoes are found

where plates meet.

Evidence Wegener used to support theory of

continental drift: • Continents fit like a puzzle • Fossil evidence• Rocks were similar in Africa and

South America• Evidence Antarctica once had a

tropical climate

How did geologists explain how the earth’s

plates moved?

Mid-Atlantic Ridge allows mantle to seep to surface through cracks and pushes plates of the earth apart.

Seafloor spreading animation

To see how geologists believe the plates moved go to the site below.

Notice the Atlantic Ocean seafloor spreading.

• Crust

• Mantle

• Outer core

• Inner core

VOLCANIC MOUNTAIN

NAMIBIA IN AFRICA

Volcanic mountains

• Formed when molten rock, or magma deep within the earth, erupts, and piles upon the surface

• Takes place where two of the earth's tectonic plates collide.

Convection currents in the Earth's mantle are what drive plate motions. Convection currents are driven by the simple fact that hot things (such as gases and liquids) rise while cool things fall.

Convection currents in the magma move the earth’s crust.

epicenterThe point on the surface of Earth that is right

above the focus of an earthquake

                                                

http://www.harcourtschool.com/glossary/science/define/gr4/epicenter4c.html

http://uc.wisc.edu/news/features/quake/pwaves.html

Earthquakes

How do we measure the intensity of an earthquake?

Seismographmeasures

or the strength of an earthquake

Seismograph records energy waves of the earth

Richter Scale

Earthquake Magnitudes Effects 

Less than 3.5 Generally not felt 

3.5-5.4 Rarely causes damage.

Under 6.0 Slight damage to well-designed buildings. 

6.1-6.9 Destructive to about 100 kilometers across

 

7.0-7.9 Major earthquake. Serious damage over larger areas. 

8 or greater Great earthquake.

Richter Magnitude Number of Earthquakes per year

1.0 to 3.9 900,000 +

4.0-4.9 6200

5.0-5.9 800

6.0-6.9 226

7.0-7.9 18

8.0-8.9 Less than 2

San Francisco Earthquake 1906

Earthquakes in the ocean cause

Destruction

30’ Wall of Water

Types of Volcanos

• Composite

• Cinder Cone

• Shield

http://images.google.com/imgres?imgurl=http://www.cotf.edu/ete/images/modules/volcanoes/typesb.GIF&imgrefurl=http://www.cotf.edu/ete/modules/volcanoes/vtypesvolcan1.html&h=236&w=265&sz=14&tbnid=qZF0vXnHnOkJ:&tbnh=96&tbnw=107&start=19&prev=/images%3Fq%3Dcomposite%2Bvolcano%26hl%3Den%26lr%3D%26sa%3DN

• have small craters in their summits

• Vesuvius, Krakatoa, Fujiyama, and Mount St. Helens

• tens of miles across and ten thousand or more feet in height.

http://images.google.com/imgres?imgurl=http://www.cotf.edu/ete/images/modules/volcanoes/typesb.GIF&imgrefurl=http://www.cotf.edu/ete/modules/volcanoes/vtypesvolcan1.html&h=236&w=265&sz=14&tbnid=qZF0vXnHnOkJ:&tbnh=96&tbnw=107&start=19&prev=/images%3Fq%3Dcomposite%2Bvolcano%26hl%3Den%26lr%3D%26sa%3DN

• consist almost entirely of loose, grainy cinders and almost no lava

• steep sides and usually have a small crater on top

• small volcanoes

http://images.google.com/imgres?imgurl=http://www.cotf.edu/ete/images/modules/volcanoes/typesb.GIF&imgrefurl=http://www.cotf.edu/ete/modules/volcanoes/vtypesvolcan1.html&h=236&w=265&sz=14&tbnid=qZF0vXnHnOkJ:&tbnh=96&tbnw=107&start=19&prev=/images%3Fq%3Dcomposite%2Bvolcano%26hl%3Den%26lr%3D%26sa%3DN

• hundreds of miles across and many tens of thousands of feet high.

• Mauna Loa

• consist almost entirely of frozen lavas

• large craters at their summits.

• largest single mountain in the world

• 30,000 +feet above the ocean floor

• 100 miles across at its base.