Dimensional Analysis  It is 93,000,000 miles to the sun. If a spaceship can travel 18,000 m/s how long would it take to get there?

Welcome to Earth Third Rock from the Sun What do we know about our planet?

Some Facts about Earth  Earth is covered with 71% oceans  Densest Rocky planet in our solar system  Our Atmosphere is 77% Nitrogen and 21% Oxygen.

Earth’s Composition (what is it made of)  34.6% Iron mostly in core Iron  29.5% Oxygen Oxygen  15.2% Silicon in most surface rocks, QUARTZ Silicon  12.7% Magnesium Magnesium  2.4% Nickel Nickel  1.9% Sulfur Sulfur  0.05% Titanium Titanium  Other elements…

The parts of Earth’s interior are  Inner Core  Outer Core  Mantle  Outer Mantle or Athenosphere  Lithosphere  Crust (includes oceanic and Continental Crust)

The Theory of Plate Tectonics  The surface of the earth is broken  The pieces are large (continent size and larger)  The plates move on a plastic layer of rock in the upper mantle  Movement is very slow, but can be measured

Types of Plate movement  Converging (compression)  Diverging (extension)  Transform Faults

Converging Plates  Two plates move together and collide  One plate moves under the other plate  Oceanic crust sinks under the continental crust in the subduction zone  The oceanic crust melts back into magma  Volcanoes are often found above subduction zones

Convergent Plate Boundaries

Are Plate boundaries Dangerous?  Mountains, earthquakes, and volcanoes form where plates collide. Millions of people live in and visit the beautiful mountain ranges being built by plate collisions. For example, the Rockies in North America, the Alps in Europe, and the Himalayas in central Asia were formed by plate collisions. Each year, thousands of people are killed by earthquakes and volcanic eruptions in those mountains. Occasionally, big eruptions or earthquakes kill large numbers of people. In 1883 an eruption of Krakatau volcano in Indonesia killed 37,000 people. In 1983 an eruption-caused mudslide on Nevada del Ruiz in Columbia killed 25,000 people. In 1976, an earthquake in Tangshan, China killed an astounding 750,000 people.

Converging of Two Continents Formation of the Himalayas

Divergent Plate Boundaries  Two plates move apart and create a gap  The center of the gap is called a Rift Valley  Magma fills the edges of the Rift valley and forms new lithosphere,  Mountains can form next to the Rift Valley  These largest of these Divergent Plate Boundaries is the Mid-Atlantic Ridge

See the formation of mountains and valleys

Transform Fault Boundaries  Two plates move horizontally past each other  The most famous in the United States is the San Andreas Fault  Since the plates move horizontally, Los Angeles is in no danger of “falling into the ocean”

The San Andreas Fault  Los Angeles is moving north 6 cm per year  In 10 million years Los Angeles will be next to San Francisco!

Location of plates and directions of movements on those plates in western United States

Evidence for Plate Tectonics  The most convincing evidence is standing on a fault line and seeing fences, buildings, and other man- made objects breaking apart from the movement. In San Francisco you can still see evidence of the 1906 earthquake

Evidence of Plate Tectonics  In the 1960s, evidence was discovered on the rock on the ocean floor surrounding the Mid-Atlantic Ridge: Alternating Bands of rock showed changes in magnetic orientation  When magma cools, it’s iron minerals align with the Earth’s magnetic field  Earth’s magnetic field has reversed direction many times, about once every 200,000 years.  The youngest rock was found near the center of the ridge, older rock farther away

Modern Evidence  GPS systems can now accurately measure small movements on the earth’s surface.  Large scale experiments have measured continents moving together  Small scale experiments have measured movement on individual faults like the San Andreas Fault in California. They can measure 0.1mm movements.

50 million years from now…  If we continue present-day plate motions the Atlantic will widen, Africa will collide with Europe closing the Mediterranean, Australia will collide with S.E. Asia, and Southern California will slide northward up the coast to Alaska.

This is the way the World may look like 50 million years from now!