Changing Earth Movement in Earth Questions to Answer

Changing Earth Movement in Earth

Questions to Answer • How does the movement of tectonic plates affect the Earth’s surface? • How does the transfer of energy relate to earthquakes and volcanoes? • How do humans prepare and respond to natural events?

Earth’s Interior

I. Earth’s Interior A. Three major layers of the Earth • 1. Crust – outermost & thinnest layer – Cool and solid rock – Divided into continental and oceanic crust • 2. Mantle – middle layer – Hot and liquid rock, 80% of Earth’s volume • 3. Core – center layer of earth – Divided into inner and outer core – Outer = hot and liquid metal (iron & nickel) – Inner = hot and solid metal “ “

Earth’s Interior • 1. Continental Crust – Less dense – Thicker, deepest beneath mountains • 2. Oceanic Crust – Beneath the ocean water – More dense – Thinner

B. Plate Tectonics • 1. Alfred Wegner introduced the idea of Pangaea (noticed coastlines fit together) – A large supercontinent • 2. Broke apart because of plate tectonics –theory that Earth’s surface is made of large moving plates – Moving of Earth’s plates – Causes the land to look different on Earth

Plate Tectonics • 3. Movement happens because Earth’s makeup – a. Lithosphere • Crust and rigid upper mantle • These are the ‘plates’, 7 large pieces & several small pieces (tectonic plates) – b. Asthenosphere • Mantle just below the lithosphere • Very liquid and slowly flowing

Plate Tectonics

C. Plate Boundaries • 1. Any place plates meet and move is known as a fault (crack in Earth) • Three Types of Plate Boundaries • a. Divergent Boundary – Move apart • b. Convergent Boundary – Move together • c. Transform Fault Boundary – Move along side (scrape past each other)

2. Divergent Boundary • Cause trenches and ridges (mid-oceanic) • Forms new crust, magma rises between • Rift valley- most studied- Mid-Atlantic Ridge

3. Convergent Boundary • Cause trenches, volcanoes, mountains • Subduction occurs – More dense oceanic crust slides under less dense continental crust

4. Transform Fault Boundary • Cause rocks to crack and break • Causes lots of earthquakes

D. Evidence • 1. Magnetic rocks in the earth change polarity

Evidence • 2. • 3. • 4. Land shapes Fossils Ancient climates

Tectonic Plates

II. Earthquakes and Volcanoes

A. Earthquakes • 1. Shaking or trembling caused by the sudden release of energy • 2. Usually associated with faulting or breaking and slipping of rocks – a. Occur at boundaries of plates – b. Release energy that create seismic waves • 3. Continuing adjustment of position results in aftershocks

Movement of Rock

Earthquakes • 4. Focus – The point underground where the rocks start to slip – Where the earthquake begins • 5. Epicenter – Spot on the surface directly above the focus (greatest damage here)

Earthquakes

Earthquakes • 6. Types of seismic waves – a. P waves (primary waves) • Fast moving longitudinal waves • First waves we detect – b. S waves (secondary waves) • Slow moving transverse waves • Second waves we detect – c. Surface waves • Rolling wave ( & ) on the surface of Earth • Cause the most destruction, collapse of buildings

Earthquakes

Earthquakes • 7. Seismology – Study of earthquakes – Use a seismograph

Earthquakes • a. Seismology – Three seismographs can tell you the location of the epicenter

Earthquakes • 8. Measured using the Richter scale

Earthquakes

B. Volcanoes • • 1. 2. A vent or hole in the crust How a volcano erupts – a. Magma collects in a chamber under the surface – b. Pressure builds up as the chamber fills – c. Pressure gets so great magma rises to the hole and comes out as lava

Volcanoes

Volcanoes • 3. Three types- determined by type of eruption – a. Shield – b. Composite – c. Cinder cone

1. Shield Volcanoes • • Eruptions are mild and occur frequently Creates buildup of a gently sloping mountain • Magma is very runny and long flowing • Largest of all volcano types

2. Composite Cone Volcanoes • Eruptions alternate between mild and explosive • Creates layers of lava, ash, & cinders, with steeper sides • Magma is thicker, cause most violent eruptions • Tallest of all volcano types

3. Cinder Cone Volcanoes • Eruptions are rare, but violent • Most of lava and ash builds up around vent –”cone” • Magma has lots of gas, causing explosion • Smallest and most abundant of all volcano types

C. Where are volcanoes? • 1. Occur at convergent plate boundaries • Oceanic-Continental plates around the Pacific Ocean • “Ring of Fire” = location of 75% of volcanoes

Where are volcanoes? • 2. Occur at divergent plate boundaries • Oceanic-Oceanic split, allowing mid-oceanic ridge to form

Where are volcanoes? • 3. Occur at hot spots • In the middle of oceanic plates, magma comes up from hole • Form a “trail” trail of volcanoes as plate moves • seamount – volcanoes forming under water • Mantle plumes

Mt. St. Helens 1980