Earth

1
Earths Dynamic Crust and Interior

• Unit 12

2

• What are some examples of evidence that the
  Earths crust moves?
• Evidence of past movements is recorded in the
  rocks.
• Crust vs. lithosphere
• - crust is the top of the lithosphere

3
Appearance of Continents

• Outlines of continents seem to fit together.
• There are similarities in minerals, rocks,
  fossils, and ages of rocks found where the
  continents may have fitted together.

4
Small Scale Changes

• Concept of original horizontality- sedimentary
  rocks and some extrusive igneous rocks, lava
  flows, form horizontal layers. These layers are
  called strata or beds.
• Layers that are no longer horizontal are called
  deformed.

5
Types of Deformities

• Folded- rock layers are bent or curved.
• Faulted- layers are offset by a fault line
• Uplift- rocks that formed under water are now
  visible above sea level.

6
Earthquakes and Igneous Activity

• Earthquakes- movement of the crust along faults.
• Energy is given off as seismic waves.
• Starts at the focus, where the waves are emitted
  from.
• Epicenter- surface directly above focus.
• Measured using seismographs.

7
Earthquake Waves

• 3 categories
• P-waves- primary waves, particles vibrate in the
  direction they are traveling
• S- waves- secondary waves, vibrate at right
  angles to the direction wave is moving
• Surface waves- P or S waves on the surface. This
  causes much of the damage.

8
Properties of Earthquake Waves

• P-waves travel the fastest. Reach the
  seismograph first.
• Velocity of wave depends on material passing
  through. More dense faster
• Increase in pressure increases the velocity.
• P-waves travel through solids, liquids, and
  gases, S-waves only travel through solids
• P-waves and S-waves bounce off some rock layers,
  identifying valuable rock and mineral resources.

9
Location of Epicenters

• Located using velocity differences in P-waves and
  S-waves. Bigger the difference in time the
  further the observer is from the epicenter.
• 3 seismograph locations must be used.
• Epicenter distances act as the radius, circles
  are drawn for each location
• Where all three circles intersect is the
  epicenter.

10
Magnitude

• Closer you are to the epicenter the greater the
  intensity
• Magnitude scale from 1-10
• Measure how much energy is being released.

11
Tsunamis

• Large wavelength ocean currents

12
Igneous Activity and Volcanoes

• Volcano- mountain composed of extrusive igneous
  rocks.
• Eruptions- giving off of gases, lava, and ash
  into the atmosphere through a vent.

13
Predicting Volcanoes

• Some success
• Satellites monitor increasing heat from the
  volcano
• Tilt meters, measure increasing slope
• Elevation, benchmarks, latitude and longitude all
  indicate an increase in elevation.
• Often times many small size earthquakes will
  occur.

14
Zones of Crustal Activity

• Zones can be located by features on Earths
  crust.
• Areas of uplift, sinking, earthquakes, and
  volcanic eruptions can be found together.
• Continental mountains, mid-ocean ridges, ocean
  trenches, island arcs.

15
Methods for Studying Earths Interior

• Readings from seismograms, when p and s waves
  arrive or dont arrive
• Results from tests done with explosives and
  nuclear bombs
• Seismic waves refract, reflect, change velocity,
  and become absorbed by various parts of Earths
  surface.

16
Zones of Earth

• Crust- outermost layer, below atmosphere and
  hydrosphere.
• Mantle- mostly solid, under crust. Thickest part
  of Earth and 80 of its volume.
• Lithosphere- uppermost layer of mantle and crust.

17

• Asthenosphere- plastic-like portion of the upper
  mantle. Most of the magma that reaches Earth
  originates here.
• Outer core- liquid, S-waves cannot pass through
  and P-waves slow down considerably.
• Inner core- solid, P-waves pick up speed.

18
Earths Crust

• Continental Crust- makes up continents and large
  islands
• Oceanic Crust- crust beneath the ocean.

19
Continental

• Thickest where highest mountains
• Composed of granitic rocks.
• Less dense

20
Oceanic

• Composed of basaltic rocks
• More dense than continental crust

21
Plate Tectonic Theory

• Earths lithosphere is broken up into plates,
  tectonic plates, and their movements produce
  major changes in the physical features on Earth.
• Move around Earth at a rate of a few cm a year.
• At least 3 times the continents have come
  together to form one large supercontinent

22
3 Types of Plate Boundaries

• Divergent- where two plates separate or diverge.
  If the divergence is in a continent a rift valley
  will form, if its under the ocean a mid-ocean
  ridge will form
• Convergent- two plates collide.
• Transform- slide past each other.

23
Convergent

• 3 types both plates have oceanic crust on top,
  both plates have continental crust, or one has
  oceanic and one has continental.
• When they converge the more dense plate slides
  underneath the less dense plate, subduction.
• Ocean trenches and island arcs can be formed.
• Orogeny- mountain building

24
Driving Forces

• Convection currents- drag or push the plates
  apart at places where plates diverge. Energy
  source is the interior of Earth.

25
Hot Spots

• Rising magma from the lower mantle remains
  stationary for millions of years. When a plate
  moves over the spot, it melts its way to the top.
• Spots can become volcanoes, lava flows, and push
  up regions of the crust to form mountains.

26
Age and Heat of Oceanic Rocks

• The further you go from the mid-ocean ridge the
  older the rock.
• The further you go the cooler the rocks are.

27
Magnetic Patterns

• Magnetic poles reverse in periods of thousands of
  years.
• There are alternating bands of polarity in the
  ocean floor.