Download Changes in Earth`s Surface

Changes in Earth’s Surface
Vocabulary
For two-column notes, underlines titles are main ideas
Scientific Theory of Plate Tectonics
•
Based on
–
Wegener’s Hypothesis
•
•
–
Sea-floor spreading
•
•
•
•
Continents drifted to their current locations
South America and Africa were once in contact
New lithosphere being created at mid-ocean ridge
Rocks are newer closer to boundary
Pattern of magnetic reversal mirrored on both side of
boundary
Pangaea
–
The original multi-continent
Changes in Earth’s Surface
Scientific Theory of Plate Tectonics
•
Evidence
•
•
•
•
Similar fossils are found on both sides of the
Atlantic where continents were once joined
Similar rocks are found on both sides of the
Atlantic where continents were once joined
Glacial deposits found in Africa
Tropical plant fossils found in Antarctica
Changes in Earth’s Surface
Scientific Theory of Plate Tectonics
• The theory of Plate tectonics was proposed in
1960s based on the theory of continental drift.
– It explains the formation and deformation of the
Earth’s surface.
• Continents are carried along on huge slabs
(plates) on the Earth’s outermost layer
(Lithosphere).
• Earth’s outermost layer is divided into 12 major
Tectonic Plates (~80 km deep). These plates
move a few centimeters per year.
• Scientific Theory of Plate Tectonics
– Causes of Plate Motion
• Mantle Convection
Mantle Convection
Draw this. Be sure to label the boundaries and
convection cells
LOCATION OF
TECTONIC PLATES
Types of plate boundaries



Divergent plate boundaries: where plates
move apart (separating plates)
Convergent Plate boundaries: where
plates come together (colliding plates)
Transform plate boundaries: where plates
slide past each other (sliding plates)
Types of plate boundaries
Divergent (Tension)
Convergent (Compression)
Transform (shearing)
Draw a picture of each
Types of plate boundaries
Types of Plate Boundaries
Divergent
• Plates move away from
each other (tension)
• New lithosphere is formed
(we know because the
rocks at the boundary are
younger than rocks further
away)
• A divergent boundary in
the ocean produces midocean ridges.
• A divergent boundary on
land produces rift
valleys.
Types of Plate Boundaries
Divergent
• As magma cools to form new lithosphere, rocks
containing iron are magnetized in the same
direction as Earth’s magnetic field.
– When the Earth’s magnetic field reverses every 70,000
years, alternate patterns of magnetism are formed.
– These patterns mirror each other across the mid-ocean
ridge
Alternating Magnetic Bands Found
in the Ocean
Types of Plate Boundaries
Divergent: ocean-ocean
Types of Plate Boundaries
Convergent
• Plates move toward each other (compression)
• Lithosphere is consumed (forced down into the
mantle)
•
•
Oceanic plates are more dense than continental plates
There are three types of convergent plate boundaries
– Oceanic-continental plate
– Oceanic-oceanic plate
– Continental-continental plate
Types of Plate Boundaries
Convergent: ocean-continental
• Oceaniccontinental plates
collide
• Oceanic plate
subducts below
continental
• Forms a
subduction zone
• Earthquakes and
volcanoes
Types of Plate Boundaries
Convergent: ocean-continental
Types of Plate Boundaries
Convergent: oceanic-oceanic
• 2 oceanic plates
collide
• One plate dives
(subducts) beneath
other
• Forms subduction
zone
• Earthquakes and
volcanoes
• Forms chain of islands
called an island arc
• Also forms ocean
trench
Types of Plate Boundaries
Convergent: continental-continental
• 2 continental plates
collide
• Neither plate wants
to subduct
• Collision zone forms
high mountains
• Earthquakes, no
volcanoes
example: Himalayas
Types of Plate Boundaries
Convergent: continental-continental
Types of Plate Boundaries
Transform
•
•
•
•
Two plates slide past each other
Lithosphere is neither consumed nor destroyed.
Responsible for most of the earthquakes
Usually occur in oceans but the most famous are
on land (like San Andreas Fault)
Types of Plate Boundaries
Transform Plate Boundary 3
Transform
What drives plate movement?
• Ultimately: heat transported from core and
mantle to surface
• Heat transported by convection
• Core is ~5,000°C and surface is ~0°C
• Where mantle rises: rifting
• Where mantle sinks: subduction zones
Plate tectonics affect climate
• Antarctica was once
tropical (fossils of palm
trees) but drifted to its
current location at the
South Pole (frozen)
• Distance between
continents affect ocean
currents, which affect
climate
Classwork 1
1. What causes tectonic plate movement?
2. Name one way in which we know that the seafloor in
the divergent boundary (spreading plates) in the midAtlantic Ocean is creating new ground.
3. ____ boundaries are most often associated with
earthquakes
4. This often occurs where oceanic and continental plates
meet at a convergent boundary
5. This often occurs where continental plates meet each
other at a convergent boundary
6. This often occurs when oceanic plates meet each other
at a convergent boundary
Copy the questions into your notebook (right-side) and answer them
Classwork 1
7. A chain of islands called an ___ ___ may be
formed where oceanic plates converge
Copy the questions into your notebook (right-side) and answer them