What is the GEOSPHERE?
All solid parts of Earth
 Rocks, soils, minerals, sediments, magma
The Grand Canyon, AZ
What are the layers of the Earth?
https://www.youtube.com/watch?v
=WwiiOjyfvAU
Layers of the Earth
• Geologists classify Earth’s layers two
ways: chemically and physically
• Chemical – by composition
• Physical- by structure
Chemical Layers of the Earth
1. Crust- O, Si, Al
2. Mantle- O, Si, Mg, Fe
3. Core- Fe, Ni
Physical Layers of the Earth
• Lithosphere
– Crust and upper mantle combined
– Broken in chunks called tectonic plates
– Oceanic plates are thinner and denser than
continental plates
• Asthenosphere
- Layer of Jello-like magma in the mantle
- Tectonic plates move due to convection
currents in the asthenosphere
Physical Layers, cont.
 Mesosphere
 The rest of the mantle;
molten rock
 Outer Core
 Liquid metal
 Surrounds inner core
 Inner Core
 Densest layer
 Solid metal
Theory of Plate Tectonics
 Lithosphere (upper mantle and crust) is
divided into pieces called tectonic plates.
 These plates glide across the underlying
asthenosphere like ice drifts across a
pond.
 Continents are located on tectonic plates
and move around with them
Seafloor Spreading
1. Magma rises from asthenosphere
2. Creates new oceanic lithosphere
3. Pushes tectonic plates apart
Seafloor-Spreading
If new crust is being created by the
process of seafloor spreading, is the
Earth growing!?
Subduction
 Subduction zones: A region where
old crust is destroyed as it is pulled
back down into the mantle
Plate Boundaries
 The area where two plates meet is called a plate
boundary.
 Most earthquakes and volcanoes occur at or
near plate boundaries
Three main types of plate boundaries:
1. Divergent- separating
2. Convergent- colliding
3. Transform- scraping past
Transform Boundaries
• 2 plates slide past each other
• Not smooth. Plates lock, and build up
tension. After too much tension builds,
the plates “snap” causing earthquakes
Divergent Boundaries
• When two plates separate
• Most common on ocean floor
• Creates Mid-Ocean Ridge
Divergence Forms New Ocean Floor
Convergent Boundaries
Three Main Types:
1. Continental & Oceanic- causes deep ocean
trench and land volcanoes Ex: Andes Mountains
2. Continental & Continental- causes large land
mountain ranges Ex: Himalayan Mountains
3. Oceanic & Oceanic- causes deep ocean trench and
island arc (chain of volcanic mountains) Ex: Mariana
trench and islands
Subduction Zone
Continental + Oceanic Crust
Continental + Continental Crust
Subduction Zone
Oceanic + Oceanic Crust (another view)
Subduction Zone
Oceanic + Oceanic Crust
Some videos for your viewing
pleasure…
Plate Movement:
https://www.youtube.com/watch?v=kwfNGatxUJI
http://www.youtube.com/watch?v=ryrXAGY1dmE&feature=e
ndscreen&NR=1
San Andreas Fault:
http://www.youtube.com/watch?NR=1&v=ZxPTLmg0ZCw&feature=endscr
een
Exit Ticket
 1. Arrows in the block diagram below show the
relative movement along a tectonic plate
boundary. What is this type of plate boundary
called?
a.
b.
c.
d.
transform plate boundary
convergent plate boundary
divergent plate boundary
subduction plate boundary
Exit Ticket
 2. When two tectonic plates collide, oceanic
crust usually subducts beneath continental crust
because oceanic crust is primarily composed of
igneous rock that is:
a.
b.
c.
d.
thin and less dense
thick and less dense
thin and more dense
thick and more dense
Exit Ticket
 3. The block diagram below shows the
boundary between two tectonic plates. Which
type of plate boundary is shown?
a. divergent
b. transform
c. convergent
d. complex
Exit Ticket
 4. The Himalaya Mountains were formed in a
collision at a:
a. divergent boundary
b. convergent boundary
c. transform boundary
d. fracture zone
Exit Ticket
 5. In which Earth layer are most convection
currents that cause seafloor spreading thought
to be located?
a.
b.
c.
d.
crust
outer core
asthenosphere
inner core
Tectonic Plates
Active Volcanoes
Earthquakes Worldwide