Transcript Plate Tectonics for Website

Plate Tectonics
What is it and why do we need to
know?
Some questions we will
answer...
·How
is the earth always changing?
·What forces inside the earth create and change
landforms on the surface?
·What is the theory of plate tectonics and how does it
work?
·What two theories help make up the theory of plate
tectonics?
·What is continental drift and sea floor spreading?
·What happens when the plates crash together, pull
apart, and slide against each other?
Key Terms: Knowledge Survey
Plate Tectonic Prior Knowledge Survey
1 = Haven’t a Clue
2 = Know I have heard it, but I can’t define it.
3 = Know I have heard it, have some sense
of its meaning
4 = Have a good sense of the meaning when
I see it or hear it
5 = Can define it and explain its meaning to
someone else
Crust
Mantle
Outer Core
Inner Core
Layers of the earth
Boundaries.asf
crust - the rigid, rocky outer surface of the Earth, composed mostly of basalt
and granite. The crust is thinner under the oceans.
mantle - a rocky layer located under the crust - it is composed of silicon,
oxygen, magnesium, iron, aluminum, and calcium. Convection (heat) currents
carry heat from the hot inner mantle to the cooler outer mantle.
outer core - the molten iron-nickel layer that surrounds the inner core.
inner core - the solid iron-nickel center of the Earth that is very hot and under
great pressure.
The Earth’s Layers
The Earth is made of many different and distinct layers.
The deeper layers are composed of heavier materials;
they are hotter, denser and under much greater pressure
than the outer layers.
Natural forces interact with and affect the earth’s crust,
creating the landforms, or natural features, found on the
surface of the earth.
Lithosphere
The lithosphere (geosphere) is the "solid" part of Earth
It has two parts, the crust and the upper mantle.
Asthenosphere
A zone of the earth's mantle that lies beneath the
lithosphere and consists of several hundred kilometers
of gooey, candy like rock.
Land and Water
Photographs of the earth taken from space show clearly tha
it is a truly a ”watery planet.”
More than 70 percent of the earth’s surface is covered
by water, mainly the salt water of oceans and seas.
What are the planets main
oceans? List them in your
notes. Hint: there are 6!
mantle convection
Heat transfer from the core to the
mantle produces slow convection
of the mantle material this is what fuels plate
movement
(in the order of centimetres per year)
Mantle convection produces the energy for
movement at the boundary between the mantle
and the crust
The Theory of Plate Tectonics
Basic Plate Tectonics Concepts
1. The outer portion of the Earth, the lithosphere (the
upper mantle and crust), is composed of rigid units called
plates.
2. Plates move slowly.
3. Most of the Earth’s large-scale geologic activity, such
as earthquakes and volcanic eruptions, occur at or near
plate boundaries.
4. Interiors of plates are geologically quiet, with fewer
and usually milder earthquakes and fewer volcanoes than
at plate boundaries.
The Earth's surface is broken into
~15 crustal plates
The Theory of Plate
Tectonics
When plates move, everything on them moves with them.
North American Plate moving west, Eurasian Plate moving
east.
Rate is about 5-10 cm/yr.
Over long periods of time, movement is large.
The Theory of Plate Tectonics
So….
Has the size of the Earth increased?
Why?
Where plates move apart or diverge, at some
other place on the Earth, they must come
together or
converge.
This is where the Earth gets exciting.
Divergent- The plates are
moving apart
This is an example of a divergent
plate boundary (where the plates
move away from each other) The
Atlantic Ocean was created by this
process. The mid-Atlantic Ridge is
an area where new sea floor is
being created.
As the rift valley expands two
continental plates have been
constructed from the original one.
The molten rock continues to push
the crust apart creating new crust
as it does.
As the rift valley expands, water
collects forming a sea.
Convergent Boundaries
Plates are destroyed!
This is a convergent plate boundary,
the plates move towards each other.
The amount of crust on the surface
of the earth remains relatively
constant. Therefore, when plates
diverge (separate) and form new
crust in one area, the plates must
converge (come together) in another
area and be destroyed. An example
of this is the Nazca plate being
subducted under the South
American plate to form the Andes
Mountain Chain.
Types of convergent
boundaries:
·Oceanic-Oceanic-Islands are created.
Oceanic-Oceanic
Mt. Fuji in Japan
Mt. Fuji in Japan
Oceanic- Continental
Continental-Continental
Mt. Everest
Continental-Continental
Transform plate boundaries
At transform plate boundaries
plates grind past each other side
by side. This type of boundary
separates the North American
plate from the Pacific plate along
the San Andreas fault, a famous
transform plate boundary that’s
responsible for many of
California’s earthquakes.