Evidence of Plate Tectonics

• Earthquakes
• Volcanoes
• Age of Sea Floor
• Topography
• Geophysical Studies (Gravity, Sonar, etc)
• Jig-Saw Pieces (Continents seem to fit together)
• Fossils (Shows how continents were once together by finding the same ones in different locations)

Continents and Plates are DIFFERENT 

Plate Tectonics

The Earth's crust is always forming new crust, hence why we DON'T have crators.

The Earth does not have crators like the Moon due to Erosion and Plate Tectonics

• There are 8-10 major plates

3 Types of Plate Boundaries

Divergent Boundaries: Plates are pulled apart.

Convergent Boundaries: Plates come together.

Transform Boundaries: Plates slide past each other back and forth.

Divergent Boundaries

Types of plates Involved    Topography             Geologic Events              Modern Examples

Ocean-Ocean             Mid-Oceanic Ridge         Sea-floor spreading,      Mid-Atlantic Ridge                                                                       Shallow Earthquakes,

                                                    Rising Magma, Volcanoes, New crust forming.

Continent-Continent     Rift Valley             Continents torn apart,          East African Rift                                   (Continental Rift)     Earthquakes, Rising Magma,                                                                                             Volcanoes, Shallow Earthquakes.

Divergent Boundaries:

Stages of Continental Rifting

Continental Rift: (East African Rift)  Earthquakes, Rising Magma, Volcanoes, Shallow Earthquake, Continents torn apart, etc. 

1. Upwarming: Materials are forming
2. Rift Valley: Volcanism is forming
3. Linear Sea: Is spreading out

Divergent Boundaries:

Mid-Oceanic Ridge

Mid-Oceanic Ridge: (A giant fissure) A long chain of volcanoes under water; Does not rise above sea level (doesn't show up on maps).

• Two plates spreading out where the Athenosphere is lifting up hot material.

Pola (or Polo) Basalts

Pola(o) Basalts: Lava cools off under water, bulbous areas that have cooled (of lava).

Convergent Boundaries:

Only boundary that has ALL Three Types

Three types:

1. Ocean-Ocean
2. Ocean-Continent
3. Continent-Continent

Convergent Boundaries has Subduction: which is the sideways & downward movement of the edge of a plate of the Earth's crust into the mantle beneath another plate. So, it forms magma. 

Convergent Boundaries:

Ocean-Ocean

Ocean-Ocean: Oceanic crust in the Lithosphere; Forms Island Arc or Volcanic Island Chain(s), and Ocean trenches.

• It forms magma, pulling water down/minerals.

Old Oceanic Crust:is cold, dense, and subducts

• Examples: Phillipines & Japan, Aleutians Islands=Volcanic Island Chains

Convergent Boundaries:

Ocean-Continent

Ocean-Continent: Ocean trenches, mountains, Stratovolcanoes (a lot of the same).

• Oceanic plate subducts under the Continental plate
• Shallow earthquakes that move inward are deeper earthquakes
• Oceanic Crust: Basalt
• Continental Crust: Aluminum, Silica, and Granite (Ex: The Andies)

Convergent Boundaries:

Continent-Continent

Continent-Continent:Only Mountains. Has deep earthquakes and deformation of rocks.

**Will NOT have one plate subducting over the Earth=Equal density/forms mountains**

Therefore, no magma/volcanoes. Example: Himalayas

Convergent Boundaries:

Ocean-Ocean, Ocean-Continent, Continent-Continent

Types of plates Involved    Topography             Geologic Events              Modern Examples

Ocean-Ocean                    Island Arcs and      Subduction, Deep             Western Aleutians

                                      Ocean Trenches     Earthquakes, Rising Magma,

                                                               Volcanoes, Deformation of rocks.

(Denser Oceanic Crust has Basalt. Continent has Aluminum, Silica, & Granite)

Ocean-Continent             Mountains,          Subduction, Deep Earthquakes,     The Andies

                                 Ocean Trenches,     Rising Magma, Volcanoes, and

                                 Stratovolcanoes            Deformation of Rocks.

Continent-Continent     ONLY Mountains     Deep Earthquakes and               Himalayas

                                                                Deformation of Rocks   (Don't have Volcanism)

Transform Boundaries

Types of plates Involved        Topography             Geologic Events              Modern Examples

    Ocean-Ocean       Major offset of Mid-Oceanic        Earthquakes           Offset of East Pacific

                                          Ridge axis.                                                 rise in South Pacific

                                                                                                               (The Eltanin)

Continent-Continent      Small deformed mountain      Earthquakes &          San Andreas Fault

                                    ranges, deformations        Deformation of rocks.

                                         along fault.

Why Plate Tectonics Occur:

Convection Cells, etc.

Convection Cells:Spread out throughout the mantle. Cool sinks and hot rises.

Subduction Zones:cool material going down b/c it's denser.

Volcanism: Divergent plate boundaries, hot materials go up and spread plates apart.

Volcanoes

Volcano(es):A Landform created when magma rises from the interior and comes out through a Vent,then called lava.It also tells us a lot about the history of the earth.

** Volcanic Eruptions gives us "Xenoliths" and tells us about the past & Volcanic Ashe preserved the "1st Homonids & others", so we have historical information **

• Vents give off heat
• A Fissure: is a large type of vent. They are very large cracks and their eruptions occur when flood basalts spread out.
• Flood Basalts: are found only in the Columbia River and Snake River Plains.

Volcanoes

The "Large Impact Theory":

Large Igneous Provinces

Large Igneous Provinces: (Bigger Flood Basalts) are found in Siberian Traps and Deccan Traps (Fissure Eruptions) and can be found under water.

Large Impact Theory: The Large Igneous Provinces formed a theory that it was the reason that it killed all of the dinosaurs 65 million years ago.

Volcanism:

Why it's important?

Volcanism 

• Helped create our atmosphere (Nitrogen, Oxygen).
• Volcanic Eruptions gives us "Xenoliths" and tells us about the past. 
• Volcanic Ashe preserved the "1st Homonids & others", so we have historical information.
• It created Lands like Hawaii and Japan
• It Nourishes plants (Island of Java) Ashe traps water & nutrients were the plants thrive off it.
• (Island of Borneo) Soil is genereated from soild particles of Bedrock.
• Geothermal Heat comes from the interior of the Earth (Iceland) has so much active Volcanism
  
• **Volcanism helped create "life" (heat,water) that were 1st found in submarine vents**

Volcanoes:

Active

Active Volcanoes:are currently erupting or erupted within the last 200 years.

• They are found on all continents except in Australia,B/c it's in the middle of a tectonic plate and no divergent boundaries
• Also found in all Oceans/Basins

Volcanoes:

Dormant

Dormant Volcanoes:Haven't been active within the last few thousand years, but it will erupt in the future.

Volcanoes:

Extinct

Extinct Volcanoes:Very unlikely to erupt within the last 10's of thousands of years.

• Erosion: All that is left is the neck of the volcano

Ways to tell if a Volcano will erupt

• Sizemographics:Used to determine (only useful for California, Sand Andreas Fault) earthquakes to see if there will be any active volcanoes because magma starts to rise and then starts to shove things out of its way.

• Gases/Gas Content: will start to emerge and kill plants. The pressure inreases w/ depth where it plugs/blocks the vent and the gas builds up=Very Explosive Eruption.

• Heating: Below the surface, measuring shallow heating b/c the magma is moving-Hot Springs

• Bulges:Magma breaking/starting to break through the surface before eruption.
  

Ways to tell if a Volcano will erupt

....Continued

Viscosity:The resistance of flow, very resistant. It depends on Temperature (things colder are more viscious) and Composition (More viscious has more Silica and doesnt break apart as easily).

**Highly Viscious=Very Eruptive**

Explosive Subduction Zones

Subduction Zones

• Pyroplastics
• Intromediate to felsic (vesicles found in the Andies)
• Water gets into the mantle and pulls water down w/it. Water causes the mantle to partially melt.
• Composite Cones/Stratovolcano
• Mantle has Silica and is Ultra-mafic
• Andestic Magma
• Intracontinental hot spot(s): Yellowstone (hot magma coming through the crust)

Volcanic Saftey Hazards

Pyroclastic:Fragmantal pieces of the preexisting rock that shoots out during eruption.The size ranges as big as a baseball to a house.

• Tephra: dust size particles instantly accumulate/cools in the air. Forms together/cements and can be turned into glass. (Air/Saftey Hazard) causes air traffic of tiny particles of gas that stays in the air for a while.
• Lahar:(major hazard) occurs on volcanoes w/ a lot of snow. Water mixed w/ pyroclastic debree and causes mud.
  

Divergent Plate Boundaries and Oceanic Hot Spot(s)

• Oceanic crust has no silica;Basaltic

• Sheild Volcanoes; low slopes

- Flood Basalts

Viscious/Viscosity in Minerals

Rhyolite: Is more viscious b/c it has more Silica and viscious eruptions w/cooler temperature.

Basalt:Mafic and Silica

Basaltic Lava

Basaltic Lava:mafic

         Subaerial (surface)                                                   Submarine (under water)

* Pahoehoe: low viscious, smoothe, ropey                   *Pillow Basalt: (comes out       

   As it cools, has ridges                                       underwater and water is alot cooler

                                                                        than Basalt and cools alot faster)

*a'a: very viscious, angular/sharp

(Both have temperature changes)

Pajoehoe is lower

                                  a'a is higher

Basaltic Lava

Continued...

Lava Tubes:Top part cools, interior keeps moving and eventually lava will go away. It shades off radiation (Collapse zones where there will be a sky light).

Scoria:Basaltic magma w/ vesicles. Gas comes out of the lava that forms bubbles that then pop while/during cooling.

Rhyolitic Lava

Rhyolitic Lava:Felsic and alot of Silica. Very explosive & very viscious.

• Hardens underneath surface
• Most of the lava solidifys w/ Granite, we don't have as much Rhyolitic lava.
• Pumice: has very small holes. Formed w/ frath/foam of Rhyolitic dust/glass, that can also float.

Rhyolitic Lava

Continued...

Andesitic: intermediate (found in the Andies)

• Has vesicles
• a'a, not pahoehoe, b/c of it's composition. a'a' has just enough silica to not have pahoehoe
• 80% of the volcanoes occur in the specific ocean & 15% in the Medetarianian and upper seas.
• The rest: Divergent ridges: Hot Spots (hot mantle material rising/Yellowstone). Mantle Plumes: oceanic plates