Download earth layers and plates 2016

Inside the Earth
Reflections
10/13 – Describe the inside of the Earth.
10/14 – Name the 6 layers of the Earth.
10/17 – Explain why the plates move.
Earth Layers
• The Earth is divided into 6 main
layers.
Inner Core
Outer Core
Inner Mantle
Outer Mantle
Crust – Oceanic and Contential
The Layers of the Earth
© Copyright 2006. M. J. Krech. All rights reserved.
The Crust
• The crust makes up 1% of
the Earth.
• The crust of the Earth is
broken into many pieces
called plates.
• Brittle rocks – Silicon,
aluminium, iron, calcuim,
sodium, potassium, and
magnesium
The Crust
The crust is composed of two rocks. The
continental crust is mostly granite. The oceanic
crust is basalt. Basalt is much denser than the
granite. Because of this the less dense continents
ride on the denser oceanic plates.
The Crust
• Outer layer
• 5-100 km thick
• 2 types of crust
– Oceanic (very dense,
made of basalt)
– Continental (less
dense, made of
granite)
Types of Crust
Oceanic crust – 7
Km thick
Made of dense
igneous rock
More dense
Continental crust –
40 km thick
Larger – under
mountains
Less dense
Oceanic and Continental Crust
The Mantle
• The mantle is the
layer below the
crust.
• The mantle is the
largest layer of the
Earth.
• The mantle is divided
into two regions: the
upper and lower
sections
The Lithosphere
The crust and the upper layer of the
mantle together make up a zone of rigid,
brittle rock called the Lithosphere.
The Lithospheric Plates
The crust of the Earth is broken into many pieces
called plates. The plates "float" on the soft, semirigid asthenosphere.
Upper Mantle
• 670 KM below the surface
• Rocks are brittle and solid
• Make up the lithosphere
• CRUST AND UPPER MANTLE MAKE UP
THE LITHOSPHERE
LOWER MANTLE
• 2900 KM below the surface
• The rocks become soft below the upper
mantle.
• Convection currents can occur because of
this fact.
• Loose SOLID
• Magnesium and iron
The Mantle
The middle mantle is
composed of very hot
dense rock. The
asthenosphere is the
reason that the crustal
plates of the Earth
move.
Asthenosphere- Partial
melted layer of the
mantle. Plates float on
the asthenosphere.
The Asthenosphere
The asthenosphere is the
semi-rigid part of the
middle mantle that flows
like hot asphalt under a
heavy
weight.
Convection Currents
The middle mantle
"flows" because of
convection currents.
Convection currents
are caused by the very
hot material at the
deepest part of the
mantle rising, then
cooling and sinking
again --repeating this
cycle over and over.
Convection Currents
The next time you heat
anything like soup or water
in a pan you can watch the
convection currents move
in the liquid. When the
convection currents flow in
the asthenosphere they
also move the crust.
Currents created by uneven
heating of substances.
!
Tectonic Plates
• Earth’s crust is broken into about 19
pieces
• These plates move on top of the
asthenosphere
The Core
• Made mostly of iron
• 1/3 of the earth’s mass
• Very hot
The Outer Core
The core of the
Earth is like a ball
of very hot metals.
The outer core
is so hot that the
metals in it are all
in the liquid state.
The outer core is
composed of the
melted metals of
nickel and iron.
Outer Core
• The outer core is
liquid.
The outer core is
made up of iron and
is very dense.
The Earth’s magnetic
field is contained in
the outer core.
5500 KM below
surface
Inner Core
The inner core of the
Earth has
temperatures and
pressures so great
that the metals are
squeezed together
and are not able to
move.
The inner core is a
solid.
6,370 KM below the
surface
The Inner Core
The inner core of
the Earth has
temperatures and
pressures so great
that the metals are
squeezed together
and are not able to
move about like a
liquid, but are forced
to vibrate in place
like a solid.
Physical Structure of the Earth
(5 Layers)
• Lithosphere- rigid outer layer (crust)
• Asthenosphere- solid rock that flows
slowly (like hot asphalt)
• Mesosphere- middle layer
• Outer Core- liquid layer
• Inner Core- solid, very dense
The Structure of the Earth and
Plate Tectonics
The Crust
• This is where we live!
• The Earth’s crust is made
of:
Continental Crust
Oceanic Crust
- thick (10-70km)
- buoyant (less dense
than oceanic crust)
- mostly old
- thin (~7 km)
- dense (sinks under
continental crust)
- young
How do we know what the Earth
is made of?
• Geophysical surveys: seismic, gravity, magnetics,
electrical, geodesy
– Acquisition: land, air, sea and satellite
– Geological surveys: fieldwork, boreholes, mines
Aim: How do Continents Drift?
I. The Continental Drift Theory
- proposed by Alfred Wegener
- theorized that the continents
floated around the planet and
moved through the oceans.
* ~ 300 mya the continents were
all together forming what was
called Pangaea = “All Land”
The Continental Drift Theory
1. Wegener believed the landmasses could all fit together.
2. Wegener did not have enough hard evidence or proof to
support his ideas.
3. It took until the 1960’s for new evidence to emerge.
4. Fossils of Glossopteris (a fern plant) are found on many
continents. Scientists think the seeds were too large to be carried
by wind, and therefore, could not explain how it traveled the great
distances between the continents today. This indicates the
continents must have been closer.
5. Fossils of Lystrosaurus (swamp-dwelling hippo-like creature)
are found on many continents. Scientists do not believe this
creature could have swam the great distances between the
continents today. This indicates the continents must have been
closer.
II. Evidence for Continental Drift
1. The Continental Puzzle
continents fit
together like a
giant puzzle
2. Matching Fossils
- Fossils of the same organisms (plants and
animals) are found on different continents.
3. Rock Types and Structures
- different mountain ranges across the
ocean have the same rock composition and
age.
Present (2013)
250 Million Years ago
Pangaea
IV. A New Theory Emerges
Theory of Plate Tectonics suggests that the
Earth’s surface is composed of rigid plates
that move, carrying the continents. (uses
Wegner’s evidence)
Plate Tectonics
What is Plate Tectonics?
• If you look at a map of the world, you may notice that some of the
continents could fit together like pieces of a puzzle.
Plate Tectonics
• The Earth’s crust is divided into 12 major
plates which are moved in various directions.
• This plate motion causes them to collide, pull
apart, or scrape against each other.
• Each type of interaction causes a
characteristic set of Earth structures or
“tectonic” features.
• The word, tectonic, refers to the deformation of
the crust as a consequence of plate
interaction.
World Plates
What are tectonic plates made of?
• Plates are
made of rigid
lithosphere.
The lithosphere is made
up of the crust and the
upper part of the mantle.
What lies beneath the tectonic plates?
• Below the
lithosphere
(which makes
up the tectonic
plates) is the
asthenosphere.
Plate Movement
• “Plates” of lithosphere are moved around by
the underlying hot mantle convection cells
What happens at tectonic
plate boundaries?
Three types of plate boundary
• Divergent
• Convergent
• Transform
Divergent Boundaries
• Spreading ridges
– As plates move apart new material is erupted to
fill the gap
Age of Oceanic Crust
Courtesy of www.ngdc.noaa.gov
Iceland: An example of continental rifting
• Iceland has a divergent
plate boundary running
through its middle
Convergent Boundaries
• There are three styles of convergent
plate boundaries
– Continent-continent collision
– Continent-oceanic crust collision
– Ocean-ocean collision
Continent-Continent Collision
• Forms mountains, e.g. European Alps, Himalayas
Himalayas
Continent-Oceanic Crust Collision
• Called SUBDUCTION
Subduction
• Oceanic lithosphere
subducts underneath the
continental lithosphere
• Oceanic lithosphere heats
and dehydrates as it
subsides
• The melt rises forming
volcanism
• E.g. The Andes
Ocean-Ocean Plate Collision
• When two oceanic plates collide, one runs over the other
which causes it to sink into the mantle forming a
subduction zone.
• The subducting plate is bent downward to form a very
deep depression in the ocean floor called a trench.
• The worlds deepest parts of the ocean are found along
trenches.
– E.g. The Mariana Trench is 11 km deep!
Transform Boundaries
• Where plates slide past each other
Above: View of the San Andreas
transform fault
Practical Exercise 2
Where will the UK be in:
1,000 years?
1,000,000 years?
1,000,000,000 years?
Volcanoes and Plate
Tectonics…
…what’s the connection?
Pacific Ring of Fire
Volcanism is
mostly focused
at plate margins
Volcanoes are formed by:
- Subduction - Rifting - Hotspots
Pacific Ring of Fire
Hotspot
volcanoes
What are Hotspot Volcanoes?
• Hot mantle plumes breaching the
surface in the middle of a tectonic plate
The Hawaiian island chain are
examples of hotspot volcanoes.
Photo: Tom Pfeiffer / www.volcanodiscovery.com
The tectonic plate moves over a fixed hotspot forming a chain of
volcanoes.
The volcanoes get younger from one end to the other.
• As with volcanoes, earthquakes are not
randomly distributed over the globe
Figure showing
the distribution of
earthquakes
around the globe
• At the boundaries between plates, friction
causes them to stick together. When built up
energy causes them to break, earthquakes
occur.
Where do earthquakes form?
Figure showing the tectonic setting of earthquakes
Plate Tectonics Summary
• The Earth is made up of 3 main layers (core,
mantle, crust)
• On the surface of the Earth are tectonic
plates that slowly move around the globe
• Plates are made of crust and upper mantle
(lithosphere)
• There are 2 types of plate
• There are 3 types of plate boundaries
• Volcanoes and Earthquakes are closely
linked to the margins of the tectonic plates