Download The Moving Crust

The Moving Crust
Topic 4
The Moving Crust
 The crust is the top layer of the Earth. It also includes the
minerals in the rocks below it.
The Crust
The Mantle
 The Earth’s mantle is made up of a plastic
rock layer
 Plastic means it is melted and gooey, but not
completely liquid
 The mantle can
flow, but very
slowly.
The Mantle
The Core
 The Core of Earth is very hot – around 6000oC
 The outer core is liquid iron and nickel around
5500oC
 The intense
heat and
pressure
have made
the inner
core a
solid ball
The Core
Continental
Drift
 The shape
of land is
constantly
changing.
Continental Drift
Evidence - Wegener
 Alfred Wegener was one
of the first scientists to
question plate movement
 He formed the Theory of
Continental Drift
Evidence
Evidence – Sea Floor Spreading
Evidence - Technology
 Sonar uses sound wave to make measurements
 Sonar identified the Mid-Atlantic Ridge
 Magnetometers detect the direction and strength
of a magnetic field
 The magnetic field of the crust in the Atlantic
sometimes pointed south, instead of north
 these are called
reversal strips
Mid-Ocean Ridges
Evidence - Technology
The Theory of Plate Tectonics
 Technology showed that the Earth’s crust is moving
 The crust is made up of plates of rock that fit like puzzle pieces
 Converging plate are coming together
 Diverging plates are moving apart
 Canadian Scientist J. Tuzo Wilson also concluded that plates can slide
past each other
Plate Tectonics
Subduction
 Subduction zones are where plates are
converging.
 Subduction is when one plate slides
underneath another.
Subduction
Plate Tectonics
Plate Movement
Plate Movement
Mariana Arc
(& Trench)
Earthquakes
Topic 5
Earthquakes
 Earthquakes are caused by sudden movements in the tectonic
plates.
 Seismic is of or having to do with the movement of tectonic
plates
 Seismologists can use seismographs to measure the intensity
of an earthquake
 It is attached to the bedrock to detect vibrations
Earthquakes
 Liquefaction is the process of a solid taking on fluid qualities,
like quicksand
 Tsunamis are huge waves that happen when an earthquake
occurs under the ocean
 (Japanese word meaning 'harbour wave')
 Avalanches or rock slides occur in mountains as a result of an
earthquake
Richter Scale
 Earthquakes are
gauged on the
Richter scale up to 10.
 Less than 2 is not
generally felt, above 8
totally destroys
communities and
structures
Table 1: Relationship between Richter Scale magnitude and energy released.
Richter Scale
2.0
5.0
Energy
Release
(J)
Comment
Smallest earthquake detectable by people.
2.8 x 1012
Energy released by the Hiroshima atomic bomb.
7.6 x 1013
About 120 shallow earthquakes of this magnitude
6.0 - 6.9 to 1.515 x
10
occur each year on the Earth.
7.7 x 1014
6.7
Northridge, California earthquake January 17, 1994.
Major earthquake threshold. Haiti earthquake of January 12, 2010
2.1 x 1015
7.0
resulted in an estmated 222,570 deaths
Turkey earthquake August 17, 1999. More than 12,000 people
7.9 x 1015
7.4
killed.
Deadliest earthquake in the last 100 years. Tangshan, China, July
1.5 x 1016
7.6
28, 1976. Approximately 255,000 people perished.
1.6 x 1017
8.3
San Francisco earthquake of April 18, 1906.
9.0
Japan Earthquake March 11, 2011
December 26, 2004 Sumatra earthquake which triggered a
4.3 x 1018
9.1
tsunami and resulted in 227,898 deaths spread across fourteen
countries
Most powerful earthquake recorded in the last 100 years.
8.3 x 1018
9.5
Southern Chile on May 22, 1960. Claimed 3,000 lives.
1.3 x 108
Seismic Waves
 Seismic waves are the energy waves that
travel outward from the source of the
earthquake.
Primary Waves
 Primary or p waves are fastest
 Can go through solids, liquids and gases.
 Compression vibrations before an actual earth quake.
Secondary Waves
 Secondary or s waves slower
 Only pass through solids not liquids or gasses.
Surface Waves
 Surface waves are the slowest
 Move like ripples - rolling motion
 Most destructive
 Created when p and s waves collide
Earthquake Location
 The time between P and S wave can help locate
the source of an earthquake
 The source of an earthquake deep in the crust is
called the focus
 The location directly
above the focus is
called the epicenter
of an earthquake
 Aftershocks are actually
smaller earthquakes
from the same focus
Earthquakes
Earthquake Location
 Primary waves are
bent or refracted as
they travel through
the Earth
 The area where they
do not come
through the other
side of the earth is
called a shadow
zone
Think about it!
 How could
the 1995
earthquake
in Kobe,
Japan have
been
recorded on
Richter
scales in
Manitoba?
Distribution of earthquakes with a magnitude less than 5.0 relative
to the various tectonic plates found on the Earth's surface.
Distribution of earthquakes with a magnitude greater than 7
on the Richter Scale.
Faults
 Rock located where tectonic plates meet is under very high
pressure
 If the rock is bent or stretched enough the rock can break
creating a fault through the crust
 There are three types of fault movement between the tectonic
plates
 Fault movement creates earthquakes
 The Big One
Faults
 Normal Faults
 Tension or pulling action, which breaks rocks apart
 North Atlantic
 Reverse Faults
 Compressive , causing rock to bend break and
buckle
 Marianas Trench, near Japan
 Slip, Strike or Transform Faults
 Shear forces causes slipping which and jagged
edges break off
 Pacific Plate
Normal Faults
Reverse Faults
Slip Faults
San Andreas