Science, Unit 3

How fast do tectonic plates move?

a few centimeters a year

Collision Zones

where two continental plates collide; continental2continetal convergent boundaries

Outer Core

the liquid layer of the Earth's core that lies beneath the mantle and surrounds the inner core; made mostly of LIQUID iron and some liquid nickel

Lithosphere

the solid, outer layer of the earth that consists of the crust and the rigid upper part of the mantle

Lithosphere

the solid, outer layer of the earth that consists of the crust and the solid upper part of the mantle; plate tectonics happen here b/c plates are on the lithosphere

Which layer has the tectonic plates?

Lithosphere

What features only appear at plate boundaries?

Mid-Ocean Ridges, Ocean trenches

Subduction Zones

areas of subduction, which typically experience volcanic eruptions; continental2oceanic convergent boundaries and oceanic2oceanic convergent boundaries

convergent oceanic-oceanic Features+Example

Features: Trenches, volcanoes, volcanic island arcs Examples: Aleutian Islands, Ring of Fire

Transform features+examples

faults ex. San Andreas Fault

oceanic crust

thinner, more dense, younger crust making ocean floor; contains more iron so it is more dense; usually 5-7km thick

4 ways Wegner supported his theory of Continental Drift

1 Some of the continents' coastlines (like South America and Africa) looked like they could fit together like puzzle pieces. There was no way this could have been a coincidence. (The Apparent Fit of the Continent) 2 The Mesosaurus was an ancient reptile that only lived in shallow freshwater, its fossils are only found on the eastern coast of South America and the west coast of Africa. It could not have swam across the salty ocean, it must have walked across South Africa and Africa while the continents were still connected. There were other fossils that this transcontinental existence applied to like the Lystrosaurus. "Identical fossils have been found in the rocks on either side of the ocean." (Fossil Correlation) 3 Mountain ranges in the North Eastern US and in the far northern part of Europe have the same type of rock and are the same age. These mountains must have once been a single mountain range because it is very unlikely for a coincidence like this to occur. "Identical rocks and mountain structures have been found on either side of the ocean."(Rock and Mountain Correlation) 4 Glaciers can only exist in very cold places and when they move they leave scratches called Glacial Striations on the rocks were they once were. Today if you look in some of the hottest places in Africa and South America, there are Glacial Striations which means these continents could not have always been in such a warm location. They had to have once been where it was cold enough to have glaciers. Also, there is a sedimentary rock called Bituminous Coal that is made of tropical plants that is NOT found in tropical places, instead it is found in places like Antarctica and Northern Europe, this means they had to have once been in a tropical location. "Coal has been found in cold areas and glacial evidence has been found in warm areas." (Paleoclimate Data)

Crust

2 types:continental and oceanic; contains oxygen, silicon, and aluminum; part of the Lithosphere; less dense than the mantle and the core

techtonic plates

A block of Lithosphere, that consists of the crust and the rigid, outer most part of the Mantle

Inner Core

A dense ball of solid iron and nickel at the center of Earth; solid b/c under a LOT of pressure

Pangea

A supercontinent containing all of Earth's land that existed about 225 million years ago.

In what way does a transform boundary differ from the other boundary types?

At a transform boundary, the plates move in a direction that is parallel to the boundary line.

What happens at the mid-ocean ridge?

Caused by Divergent Boundary under the ocean; molten magma rises from the mantle to make new oceanic crust; the newer the crust, the closer it is to the ridge

Which boundary or zone adds new material to the lithosphere (the hard outer crust of the Earth)?

Divergent boundary

What causes Earth's plates to move continuously?

Earth's plates move continuously in response to slow-moving convection currents in the mantle as well as b/c of slab push and ridge pull (see slab pull and ridge push cards)

Theory of Continental Drift

Idea that at one point in time all of the continents were one super continent called Pangea and have since drifted to their current locations

divergent features+examples

Mid-Ocean Ridges; Rift Valleys ex. Mid-Atlantic Ridge; East African Rift Valley

Plates are on the ______ and "float" on the _______

Plates are on the lithosphere and "float" on the asthenosphere

Ridges v Trenches

Ridges are formed at divergent boundaries and usually happen far from land Trenches are formed at subduction zones (convergent boundaries from continetal2oceanic and oceanic2oceanic) often closer to land; volcanic activity happens near these

How do scientist study the mantle if they cannot dig deep enough to get to it?

Sometimes mantle rock comes to the surface. Melted rock from mantle comes out via volcanoes and divergent plate boundaries.... scientist often study the ocean floors to study mantle b/c of this.

Which type of plate boundary or zone would be most likely to lead to above-ground volcanic activity?

Subduction zone; when the plate subducts the magma may find a place to come out and form volcanic mountains or islands

Asthenosphere

The soft layer of the mantle on which the lithosphere floats; contains magma; convection currents happen here

Mesosphere

The strong, lower part of the mantle between the asthenosphere and the outer core

Mesosphere

The strong, lower part of the mantle between the asthenosphere and the outer core;

describe a trench relationship w/ something else formed by _______

Trenches are often found near something else formed formed by subduction. The subduction often causes a trench and another feature. For example, when the Nazca Plate subducted with the South American Plate, it formed the Peru-Chile Trench and the Andes Mountains which are volcanic mountains.

Convergent Oceanic-Continental Geologic Features Created + Ex.

Trenches ex. Cascadia Trench Volcanic Mountains ex. Andes Mountains

Collision Boundary

When two continental plates collide together

convection current

a current caused by the rising of heated fluid and sinking of cooled fluid; the hot magma in the mantle becomes less dense as it rises, then it cools, becomes more dense, and sinks

divergent boundary

a plate boundary where two plates move away from each other exposing the magma in the asthenosphere; forms rift valleys (land) and trenches and ridges (ocean); new lithosphere forms from the exposed magma @ divergent boundaries like Mid-Ocean Ridges; ex. of Mid-Ocean Ridge = Mid Atlantic Ridge which was formed by the South American plate and the African plate splitting apart

transform boundary

a plate boundary where two plates move past each other in opposite directions; causes earthquakes; The North American Plate and the Pacific Plate form a famous transform boundary. The fault line is called The San Andreas Fault. It is the cause of most of the earthquakes in California.

convergent boundary

a plate boundary where two plates move toward each other; 3 types:oceanic2oceanic, continetal2contintental; oceanic2continental; in continental2continetal continetal crust collides w/ continetal crust... plates don't really subduct... they collide... pressure of plates not being able to subduct makes them form mountains (useualy fold mountains which can only B found @ plate boundary from continental2continental).... ex. when the Indian plate crashed into the Eurasian plate it formed the Himalayan Mountains; Continetal2Ocean: more dense oceanic plate subducts... magma may find a place to escape to form volcanic mountains (ex. The Andes Mountains which formed when the Nazca plate subducted w/ the South American plate); Oceanic2Oceanic the denser of the 2 oceanic plate subducts... happens under the ocean.... can create Volcanic Islands b/c when plates subduct magma may find a way to come out.... ex. The Japanese Islands which were formed when the Philippine Plate subducted w/ the Eurasian Plate; trenches happen @ subduction zones

Himalaya Mountains were formed by

collision boundary

The highest mountains in the world are the Himalayas, at the border between the Indian and Eurasian plates. The Himalayas formed in a ________________.

collision zone

What force drives the movement of plates in the mantle?

convection currents; slab pull (during subduction, oceanic lithosphere @ the edge of the plate sinks into the mantle b/c it is so dense, as the plate sinks it pulls the rest of the plate down w/ it); ridge push (@ mid-ocean ridges where new less-dense, warmer oceanic lithosphere forms... it is less dense so it floats higher on asthenosphere compare to the older denser lithosphere.... gravity pulls the new lithosphere down which slides the plate away from the mid-ocean ridge b/c it is being pulled w/ the new lithosphere)

4 types of plate boundaries

convergent, divergent, and transform, collision boundaries

Island Arcs

formed at convergent boundaries when oceanic crust subducts w/ oceanic crust or at Hot Spots; magma may find a place to come out to form a series of volcanic islands like the ones in The Ring of Fire around the Pacific Plate (convergent boundary)

faults

found at transform boundaries; A fault is formed in the Earth's crust as a brittle response to stress. Generally, the movement of the tectonic plates in a transform boundary provides the stress, and rocks at the surface break in response to this.

Alfred Wegener + why was his theory not accepted

german scientist who came up w/ the Theory of Continental Drift.... he was not believed b/c he died too early to prove WHY the continents were separating ALSO it was such a radical idea that the continents were actually moving people were more hesitant to accept what seemed like a crazy idea that flew in the face of everything they knew

Hot Spots

happens in the middle of the plate @ a thinner area in the crust where magma breaks through (typically @ oceanic crust b/c thinner); magma rises from a MANTLE PLUME and breaks through the crust to form a volcano; 1 hot spot can form several volcanoes b/c plates are always moving so as the plate is dragged over the hotspot while it moves (plates are in constant motion) another volcano is formed; ex. Hawaii and Yellowstone

Mantle

most of earth's mass; magma comes from mantle; exists in ASTHENOSPHERE and mesosphere; the upper-most part is solid and exists in the Lithosphere; contains Magnesium and less aluminum than the crust so it is denser; convection currents happen here

Convergent Continental-Continental Features+Example

mountains (particularly Fold Mountains) ex. Himalayan Mountains, Appalachian Mountains

Divergent boundary pulls apart, magma flow up to create

new seafloor

Subduction

process where the denser oceanic crust sinks under the less dense continetal or oceanic crust; volcanic activity is most likely to happen in subduction zones b/c convection currents in mantle pull plates together 4 subduction and magma from mantle may find a place to come out 2 form volcanic structures; trenches also happen in subduction zones

Glacier Striations

scratches left on the surface of rocks as glaciers move over the surface.

Laurasia

supercontinent that contained North America, Europe, Asia; existed at the same time as Gondwana

Gondwana

supercontinent that existed at the same time as Laurasia (did NOT contain North America, Europe, and Asia..... it DID contain India)

theory of plate tectonics

the theory that pieces of Earth's lithosphere are in constant motion, driven by convection currents in the mantle and/or ridge push and/or slab pull

continental crust

the thick part of the earth's crust that forms the large landmasses; less dense than oceanic crust; up to 100km thick

Asthenosphere

the upper layer of the earth's mantle, below the lithosphere, and convection is thought to occur.

Seismic Waves

vibrations that travel through Earth carrying the energy released during an earthquake

Hotspot features+examples

volcanic islands, island arcs; ex. Hawaii

What features are commonly found at plate boundaries?

volcanoes; earthquakes

Ridge Push

when new less dense lithosphere forms at ridges at the edge of ridges, it is higher on the asthenosphere than the older lithosphere.... gravity pushes the newly formed lithosphere down and the rest of the ridge is pushed along with the newer lithosphere; Mid-Ocean ridges happen here

slab pull

when subduction happens, some oceanic lithosphere gets pulled into the mantle and as it sinks, the rest of the plate gets pulled with it; trenches are found near here