Download Topic 11A: Plate Tectonics, Part II Online Lecture: Basic Ideas of

11A_2 – Slide 1
Topic 11A:
Plate Tectonics, Part II
Online Lecture:
Basic Ideas of Plate Tectonics
How We Know About the Interior of the Earth 11A_2 – Slide 2
No one can go more than about 10 miles down into the Earth.
Information about the interior comes from indirect sources like
using earthquake waves to do an “ultrasound” of the Earth.
11A_2 – Slide 3
Layers of the Earth
○ The cooler, solid, lower density outer layer of the earth
(the lithosphere) floats on the warmer, semi-solid, higher
density layer below it (the mantle).
○ The lithosphere is broken
into pieces or parts
called “plates.”
○ MOR & Trenches are at
the edges (boundaries)
of the plates
Edges (boundaries) are
where all the action is:
earthquakes, volcanoes,
rising mountains, etc.
Plates are "pieces" or "parts"
of the Earth's outer layer,
Plates
the lithosphere ("crust"). MOR
Trench
Mantle
Core
The Plates
11A_2 – Slide 4
Edges are MOR & Trenches
Trenches are
places where
2 plates collide.
MORs are places where
2 plates go apart.
11A_2 – Slide 5
Plates Are Pieces of
the Earth’s Lithosphere (and “Crust”)
○ The top of the lithosphere is composed of “crust:”
– Continental: granite, lower density
– Oceanic: basalt, higher density
○ The mantle can
flow slowly (“ooze”).
One plate can include
both continental and
oceanic lithosphere.
Trench
1 Plate
Oceanic Crust
Continent
Continental
Crust
Lithosphere
Mantle
11A_2 – Slide 6
Basic Picture of Plate Tectonics I
New ocean floor
being made at MOR
Phillipines
Plate
bd
Pacific
Plate
Nazca
Plate
s
t
uc
su
Old ocean floor
being destroyed
su
Mantle
Plates are pushed by magma
currents (the convection cells) of
the mantle – a few inches a year.
South
America
bd
u
ct
s
Old ocean floor
being destroyed
11A_2 – Slide 7
Basic Picture of Plate Tectonics II
Volcanic
Islands
Trench
Continental
Lithosphere
Ocean Litho.
Note: There are not trenches next to all continents.
Ocean crust also pushes continents around.
es
Convection
Cell
ak
Convection
Cell
qu
Ea
rt h
rt h
Ea
qu
ak
e
s
Trench
Mid-Ocean
Ridge
Volcanic
Mountains