Chapter 3 Flashcards
What is the theory of plate tectonics(no history)
Theory that earths lithosphere is broken into pieces or plates
Why do we study plate tetecnoics
Has led to many tragic events
1985 Earthquake killed more than 9,00 people in mexico city
Two months latera volcano erupted killing more than 23,000 people
These two events occured in the ring of fire
A zone of intense volcanic activity around the pacific ocean
Explain Average Rate of movement of plates and know the plates
(Loook at notes)
Explain Continental Drift
Early idea relating to plate tectonics
Began in 15th century by leonardo de vinci
Alfred Wegener is accrediting with the hypothesis
Proposed: All landmasses were once a single super continent- Pangea
Present continent’s have broken up from Pangaea and moved apart since then
In 1937 SOuth african Geologist: Alexander Du Toi supported Wegener and proposed what?
1937 Another Geologist supported Wegner and proposed two landmasses at the beginning
1.Gondwana: Southern Landmass
Australia, Africa, Antarctica, south América
2.Laurasisa: Northern Landmass
-North America, Greenland, Europe, Asia
Evidence for Continental Drift(First Two)
- Fit of shorelines of continents
Close resemblance between coastlines (south América and Africa)
2.Similarity of rock sequences and mountains ranges
If continents were together, rocks and mountain ranges of same age in adjoining location could closely match
Evidence for Continental Drift(First Three)
3.Glacial Evidence
Similar evidence of glaciers found in all continents
4.Fossil Evidence
Fossils of floral plants are found in all five continents
- Paleomagnetism and Polar Wondering
They confirmed that contients have indeed moved in the past based on studies of earths magnetic field
Evidence For Sea Floor Spreading(1950s)
1950s discovered that Midatlantic ridge was part of a wordl wide oceanic rudge system
b. Oceanic ridges(check notes for visual) are charactrized by
1. High heat
2.Basaltic volcanism(lava flowing)
3. Seismicity(frequency of earthquakes in a region.)
Who discovered sea floor spreading
Harry H. Hess propsoed the hyphtesis in 1962
Stated
Hot magma comes up from the mid oceanic ridges
creating a new oceanic crust
old crust is pushed furtehr away on both sides
Old crust is subucted back into the mantle where it is heated and recycled
(Watch sea flooor spreading video for kids MIAACADEMY)(look at notes)
More in depth of the Plate Tectonics Theory
The lithosphere(crust+mantle) is brken in pieces or plates
Plates vary in sizes
continental crust 250 km (thick less dense)
Oceanic crust 100 km(thinner more dense and heavy)
PLates move on hotter weaker astenosphere
As they move on it they
1. Separate
2.Slide pass eachother
3. Collide and are subducted into the mantle at oceanic trenches
Plate tectonites confirms theories of continental drift and sea floor spreading
Explains earthquakes, volcanism, mountain building
Plate Boundaires
Plates move relative to one anther and have three different boundaries
1.Divergent Boundary
2.Convergent Boundary
3.Transform Boundary
Divergent Boundary
Where plates are spreading and new ocean lithosphere forms
Mainly occurs at ocean ridges
High heat flow
Basaltic flow(check notes)
Going away from each other <- ->
Convergent Boundary
(Name Three collison)
Where plates come together or collide
Old oceanic crust will be destroyed
Area of earthquakes -> <-
1.Oceanic-Oceanic Convergent Boundary
-One plate subducts beneath the other
the one that suducts gets heated and melted into magma
-It then rises through rocks to form volcanic
2.Oceanic- Continental Boundary
These two plates meet
The ocean plate is densier so it subducts
Volcanic arcs r formed(Check notes)
Continental- Continental
2 of these plates meet
One of the plates go down but there is confusion which causes a struggle which is dangerous
Transform Boundaries
Where plates slide past eachother->
Lithosphere is neither created or <-destroyed
Instense shatter of rock
Earthquakes
How are Plate Tectonics keep alive
- Convection Cells
Where the warm material is rising in the center and cold material is sinking
