• What do you think these continents looked like 200 million years ago?

• Back in the 1900s, Alfred Wegener, german scientist, noticed that Earth’s continents looked like pieces of a puzzle. When he put them together they seemed to form one large continent. He named this continent PANGEA

What two other reasons did they use to say that the continents were all once connected, besides

they look like puzzle pieces.

Alfred Wagener is credited with the theory of continental drift.

Plate Tectonics• The world is

made up of a bunch of ‘plates’ that move over time in different directions and at different rates.

Lithosphere-includes the crust and part of the mantle, this is what is divided into the tectonic plates.

Asthenosphere- the layer under the lithosphere which allows the plates to slide, made up of mantle.

• They glide across the Earth much like ice drifts across a pond.

• Geological activity that happens on the Earth’s surface happens at the boundary between the plates.

What do I mean by geological activity?

• Most are located with oceanic crust

• Earthquakes and Tsunamis are caused by this type.

• Lithosphere is pulled apart, as this happens the block between the two pulling surfaces cracks and falls allowing magma to seep up to the surface.

• Two plates slide past one another, lack large surface features.

• Most famous is San Andreas Fault in California. Unlike popular belief California will not fall off into the ocean…however, Los Angeles will eventually be located beside San Francisco!

• Sliding plates cause lots of earthquakes and sometimes Tsunamis!

• Places where plates crash or crunch together are called convergent boundaries

• Take a look at the edge of the plates…the continental plate has folded into a huge mountain range while the oceanic plate is digging deep into the ground.

• Earthquakes, mountains, Tsunamis and volcanoes are also caused by this type of boundary!

MountainsMountains

• Formed when two plates push against one another, at a convergent plate boundary, the crust becomes thicker and begins moving upward.

• Some Mountains are still growing (Mt. Everest) while others are slowly eroding away.

Appalachian Mountains

Rocky Mountains

Tsunami

• a series of water waves caused by the displacement of a large volume of water by an earthquake, volcanic eruption, or an undersea landslide.

How Tsunami’s Become Destructive

http://www.pbs.org/wgbh/nova/earth/anatomy-tsunami.html

• They occur mostly at the boundaries of tectonic plates

• Fault- a break in the Earth’s crust where the crust slide against one another.

• Earthquakes- vibrations of the Earth’s crust caused by slippage along a fault

• As plates move their edges experience immense pressure and the rocks eventually break.

• Earthquakes happen all of the time, most are so small that we don’t even feel them.

• Tremors- refers to the shaking that is felt with an earthquake

• Seismology is the study of earthquakes!– The Richter scale is used to measure the amount of

energy released by an earthquake, called magnitude.– magnitude 2 or lower earthquakes we rarely ever

even feel them– magnitude 7 and over causing serious damage over

large areas. – Largest magnitude ever recorded was a magnitude

9.5!

Earthquake Hazard

• Scientists still cannot predict when earthquakes will take place.

• We do know where they are most likely to occur.

Turn to page 94 in your book!

Earthquake Proof Areas

-Looking at the highest hazard level areas in the United States, we can help people prepare for the possibility of Earth quakes.

-Areas prone to Earth quakes, they build buildings, bridges, homes that are at least partially earthquake resistant.

-these buildings are usually slightly flexible so that they can sway with the ground motion.

All About Volcanoes• Volcano- a mountain built from magma

(melted rock) that rises from the Earth’s interior to its surface.

• Usually located near tectonic plate boundaries

• Located on land and in the ocean.– Volcanoes create islands!

• Most active volcanoes are located in the Pacific Ocean on the ‘ring of fire’.

RING OF FIRE• Contains 75% of the world’s active

volcanoes

• Located right on a plate boundary.

• There are many different types of Volcanoes believe it or not.– Composite Volcanoes have layered ash,

cinders and lava (Mt. St. Helens, Mount Rainier)

– Cinder cones are the smallest and most abundant. Violent eruptions occur and usually only last for a short time

Volcanoes can come in many shapes and sizes.

Effects of Volcanic Eruptions

• Volcanoes erupt when the pressure of the magma inside builds up and can not be contained inside any longer.

• Clouds of hot ash, dust, and gases can flow down the slope of a volcano at speeds up to 4,400miles/hour!

• They can completely devastate an entire city in split seconds.

• Major volcanic eruptions can change Earth’s climate for years!– Ash and gases reduce the amount of sunlight that

reaches the Earth’s surface– Can cause drops in temperature world wide

• The forces at the boundaries of plate tectonics shift rocks around, bringing some to the surface and sending others below.

• Weathering- the breaking down of Earth’s rocks by natural processes

• Erosion- the removal and transport of surface materials– Water and wind erosion are the two most common ways to

remove and transport materials.– Remember Rocky Mountains vs. Appalachian Mountains!