Download inside earth

INSIDE EARTH
Big Idea: Students will understand Earth's internal
structure and the dynamic nature of the tectonic plates
that form its surface.
Objective 1: Evaluate the source of Earth's internal heat and the evidence of
Earth's internal structure.
Objective 2: Describe the development of the current theory of plate tectonics
and the evidence that supports this theory.
Objective 3: Demonstrate how the motion of tectonic plates affects Earth and
living things.
Earth’s Internal Heat



Earth is HOT, temperature
increases 25◦ C per km of
depth
Core temperature  6,000◦ C
(about 10,800◦ F)
Why is this heat important?
 Powers
most geological
processes
 Drive plate tectonics
Source of Earth’s Heat

Heat of formation
 Energy
of Earth’s formation
converted into heat energy
 e.g. kinetic energy of impacts

Radioactive decay
 Heat
is a by product of
radioactive decay
 Slows down Earth’s cooling –
almost at a steady
temperature
Earth’s Layers



Earth is layered, it
is not the same
throughout
How did the layers
form? ???
Layers defined by
composition or
physical properties
Compositional Layers
Compositional Layers

Core
 Metallic,
extremely
dense
 Solid iron inner core
 Liquid nickel-iron
alloy outer core
 Makes Earth’s
magnetic field
 3,500 km thick
 ~ 4,400-6,000◦ C
Compositional Layers

Mantle
 Silicate
rocks rich in
magnesium and
iron
 Dense, semi-solid
 2,900 km thick
 ~ 500-4,400◦ C
Compositional Layers

Crust
 Variety
of igneous,
metamorphic and
sedimentary rocks
 Solid low-density
plates, float on
mantle
 5-70 km thick
 < 0-500◦ C
Evidence of Earth’s Structure

Seismic studies (seismology)
 The
scientific study of
earthquakes and seismic waves
as they move through and
around the Earth

Seismograph / seismometer
 Instrument
that measures
motions of the ground
Evidence of Earth’s Structure

Seismic waves
 Waves
of energy caused by
the sudden breaking of rock
within the Earth

P-waves (primary)
 Fastest
body wave
 Can move through liquid and
solid

S-wave (secondary)
 Slower
body wave
 Can only move through solids
Evidence of Earth’s Structure

P-waves

Bend at core


Speed up at inner core


Outer core must be
liquid
Inner core is solid
S-waves

Move through the
mantle


Mantle must be solid
Do not pass through
the core

Core must have a liquid
layer
Evidence of Earth’s Structure


Composition of
meteorites
Similar in
composition to
Earth’s interior
 Iron
meteorites =
core
 Stony iron meteorites
= deep mantle
 Stony meteorites =
crust and upper
mantle
Evidence of Earth’s Structure

Samples of the crust
and mantle
 Scientists
drill and
take samples of the
crust
 Currently
trying to drill
to the mantle
 Can’t
drill to mantle,
but it is exposed in
some places
 Volcanic eruptions
Layers Based on Physical Properties

Lithosphere
 Crust
and
uppermost rigid
mantle
 Hard and rigid
 Divided into plates
 Can break = ?
Earthquake
Layers Based on Physical Properties

Asthenosphere
 Hot,
mobile part of
upper mantle
 Semi-solid = plastic
A
solid that can
flow e.g. silly putty
 Lithosphere
floats
on top
 Source of most
magma
Layers Based on Physical Properties

Mesosphere
 Dense,
solid rock
 Hotter than upper
mantle, but
pressure is greater
so it is rigid
Layers Based on Physical Properties

Outer core
 Dense,
liquid metal
 Flow creates
magnetic field

Inner Core
 Extremely
dense,
solid metal
 Pressure keeps solid
Evidence of Physical Layers

Seismic waves
Can also detect boundaries between
layers
 Speed matters! E.g. waves slow in
asthenosphere = semi-solid


Density


Magnetic field


Based on comparisons to Earth’s
average density and meteorite density
Evidence of flow in outer core
Observations and experimentation!
Movement of Earth’s Heat

Conduction
 Direct
transfer of heat
through molecules

Convection
 Transfer
of heat through
movement
 Majority of heat
transfer
http://earthguide.ucsd.e
du/eoc/teachers/t_tecto
nics/p_convection2.html
INSIDE EARTH
Big Idea: Students will understand Earth's internal
structure and the dynamic nature of the tectonic plates
that form its surface.
Objective 1: Evaluate the source of Earth's internal heat and the evidence of
Earth's internal structure.
Objective 2: Describe the development of the current theory of plate tectonics
and the evidence that supports this theory.
Objective 3: Demonstrate how the motion of tectonic plates affects Earth and
living things.
Continental Drift

Alfred Wegener


Continental Drift
Hypothesis


German scientist that
proposed the Continental
drift hypothesis in 1912
The continents once were
a single landmass before
breaking apart and
drifting to their present
locations
Single landmass was
later named Pangaea
https://www.youtube.com/watch?v=T1-cES1Ekto
Evidence

Fossil record



Ancient fossils of extinct plants
and animals found in rocks of the
same age on different continents
Mesosaurus: extinct land reptile
fossil found in E. South America
& W. Africa
Ancient climates



Warm climates show deposits
from ancient glaciers
Cold climates containing ancient
coral reefs and coal deposits
(from warm tropical swamps)
http://www.geo.arizona.edu/~r
ees/atlanticcontinentsrev.mov
Evidence


Geometric fit of continents
Geologic record


Identical rocks of the same type
and age on different continents
Mountain ranges with the same
rock types, structure and ages on
opposite sides of the Atlantic
Problems with Continental Drift

Wegener could not explain HOW the continents
moved
Seafloor Spreading


In 1960, Harry Hess, a Princeton geologist, proposed the
“HOW” of Continental Drift
Seafloor spreading

A process that occurs at mid-ocean ridges, where new oceanic
crust is formed through volcanic activity and then gradually moves
away from the ridge. It ultimately subducts back into the mantle
at oceanic trenches.
https://www.youtube.com/watch?v=GyMLlLxbfa4
Evidence of Seafloor Spreading

Mid-ocean ridges




Underwater mountains where
magma rises up and pushes
the seafloor outward
The lava cools and becomes
new oceanic crust
Youngest, hottest part of the
seafloor
Oceanic trenches (deep-sea)



Long, narrow depressions on
the seafloor
Occur where two plates
converge (meet) and one
subducts under the other
Oldest, deepest, coolest part
of the seafloor
Evidence of Seafloor Spreading

Magnetic striping




Ancient magnetism shows
reversal of Earth’s magnetic
field (flips from N to S)
Occurs on average every
500,000 years
As lava at a mid-ocean ridge
cools, magnetite crystals line up
in the magnetic field like
magnets (pointing N)
This is recorded on the ocean
floor as stripes, with mirror
images on either side of a midocean ridge
https://www.youtube.com/watch?v=BCzCmldiaWQ&list=PLRDOLHrgGYUvmqLQhZ5jG1QdrMJibRAD
Evidence of Seafloor Spreading

Age of the
seafloor

Seafloor is
youngest at
the mid-ocean
ridges and
becomes
progressively
older with
distance from
the ridges
Theory of Plate Tectonics


The Earth’s surface is divided
into several moving, crustal
plates composed of oceanic
lithosphere and thicker
continental lithosphere, each
with its own kind of crust
Types of crust


Oceanic- younger, thinner, 5 miles
thick (oldest  200 million years
old)
Continental- older, thicker, up to 60
miles thick (oldest  4 billion years
old)
Evidence for Plate Tectonics

Distribution of earthquakes and volcanos
 Both
occur at plate boundaries
Evidence for Plate Tectonics

Hot spots (mantle
plumes)
 Volcanic
regions fed
by spots of mantle
upwelling
 Plates move over these
spots, creating volcanic
island chains
 Show rate and
direction of plate
movement
 e.g. Hawaiian Islands
INSIDE EARTH
Big Idea: Students will understand Earth's internal
structure and the dynamic nature of the tectonic plates
that form its surface.
Objective 1: Evaluate the source of Earth's internal heat and the evidence of
Earth's internal structure.
Objective 2: Describe the development of the current theory of plate tectonics
and the evidence that supports this theory.
Objective 3: Demonstrate how the motion of tectonic plates affects Earth and
living things.
Lithospheric Plates




Plates are made of crust and rigid upper mantle
Float on top of the asthenosphere
Move at a rate of a few centimeters a year
2 types
Continental plates – granitic rocks, less dense, older
 Oceanic plates – basaltic rocks, denser, younger

Major Plates

https://www.youtube.com/watch?
v=uGcDed4xVD4
7 major plates
1.
2.
3.
4.
5.
6.
7.

African Plate
Antarctic Plate
Eurasian Plate
Indo-Australian Plate
North American Plate
Pacific Plate
South American Plate
Plate boundaries
 The
border between adjacent plates where they interact
Convergent Boundaries

2 plates are colliding and
one plate subducts into the
mantle under the other
a)
b)
c)
Continental/Oceanic produce a trench and
volcanic mountains
Oceanic/Oceanic produce a trench and an
island arc
Continental/Continental produce folded mountains
Divergent Boundaries




2 plates are moving apart
The asthenosphere moves
up to fill in the space
Ocean: produces
underwater mountains (midocean ridges & seamounts),
rift valleys, & islands
Land: produces rift valleys,
rift lakes & fault block
mountains
Transform Boundaries



2 plates slide past each
other or move the same
direction, just at
different speeds
Produce transform faults.
e.g. San Andreas Fault
Causes of Plate Movement

Gravity
Ridge-push: plates are at higher
elevations at mid-ocean ridges and
are pulled down and away from the
ridge by gravity
 Slab-pull: as plates are subducted,
gravity pulls the plate down into the
mantle and the plate moves behind


Density
Less dense lithosphere floats on
denser asthenosphere, allowing
movement
 Differences in density allow plates to
subduct beneath one another

Causes of Plate Movement

Convection Currents
 As
material warms, it becomes less dense so it rises and
spreads out.
 As it spreads out, it cools and sinks, only to be heated
and rise again.
 Plates may be dragged along on the current
http://earthguide.uc
sd.edu/eoc/teacher
s/t_tectonics/p_conv
ection2.html
https://www.youtube.c
om/watch?v=ryrXAGY
1dmE#t=37
Map Assignment:
draw in plate boundaries
color the plates different colors
write in name of plate and draw in arrows to show direction of movement.
Earthquakes

Earthquakes transfer energy from
the Earth’s interior to the surface as
seismic waves (mechanical energy)



Rayleigh surface waves do the most
damage
Pacific Ring of Fire – 90% of world’s
earthquakes occur in this belt
Fault zones – fractures in rock, due
to tectonic stresses e.g. San Andreas
fault


Not always at boundaries (e.g.
Wasatch fault)
https://www.youtube.com/watch?v=R8
oXqU6ccsY
Volcanos

Hot, less dense magma rises due to density and erupts,
transferring:
 Heat
as flowing magma
 Energy as explosions (mechanical energy)

Subduction zone
 Subducting
plate
melts, the water
in it melts
surrounding
magma, which
rises and erupts
Credits

http://www.livescience.com/29054-earth-core-hotter.html

http://www.soest.hawaii.edu/GG/FACULTY/POPP/Oct07_Ch_12.pdf

http://www.geology.sdsu.edu/how_volcanoes_work/Heat.html

http://geology.com/meteorites/meteorite-types-and-classification.shtml

http://www.sciencephoto.com/

http://scienceline.ucsb.edu/getkey.php?key=3665

http://commons.wvc.edu/rdawes/G101OCL/Basics/earthinterior.html

http://faculty.icc.edu/easc111lab/labs/labi/prelab_i.html

http://www.columbia.edu/itc/ldeo/v1011x-1/jcm/Topic3/Topic3.html


http://www.dailymail.co.uk/sciencetech/article-2297050/Massive-volcaniceruptions-wiped-HALF-life-Earth-200-million-years-ago.html
http://www.huffingtonpost.com/2013/09/20/photos-oflava_n_3950497.html

http://earthsky.org/earth/what-is-the-source-of-the-heat-in-the-earths-interior

http://www4.uwsp.edu/geo/faculty/ozsvath/lectures/Continental_Drift.htm

http://www.geology.sdsu.edu/how_volcanoes_work/Heat.html

http://www.nature.nps.gov/geology/usgsnps/animate/pltecan.html

https://geoinfo.nmt.edu/resources/uranium/basics.html

http://mail.colonial.net/~hkaiter/ContinentalDrift.html

http://astrobioloblog.wordpress.com/2011/10/10/how-the-earth-was-born/

http://facweb.bhc.edu/academics/science/harwoodr/geol102/Study/origin.
htm

http://www.sciencedaily.com/articles/o/oceanic_trench.htm

http://www.space.com/17777-what-is-earth-made-of.html

http://www.sanandreasfault.org/Tectonics.html

http://pubs.usgs.gov/gip/dynamic/inside.html

http://www.pbs.org/wgbh/nova/education/activities/2515_vesuvius.html

http://www.merriam-webster.com/concise-images/73583.htm

http://www.divediscover.whoi.edu/tectonics/tectonics-subduct.html

http://maggiesscienceconnection.weebly.com/layers-of-the-earth.html

http://www.columbia.edu/~vjd1/driving_forces_basic.htm

http://www.geo.mtu.edu/UPSeis/studying.html

http://web.ics.purdue.edu/~braile/edumod/waves/WaveDemo.htm

http://www.geo.mtu.edu/UPSeis/waves.html


http://www.cyberphysics.co.uk/topics/earth/geophysics/Seismic%20Waves%
20Reading.htm
http://www.awi.de/en/news/focus/2012/the_100th_anniversary_of_alfred_
wegeners_continental_drift_theory/picture_gallery/