Our Changing Earth

1
The Changing Earth
StarrySkies.com
2
LAYERS OF THE EARTH
Core
Mantle
Crust
3

• The Earths Layers
• Crust
• Outer layer
• Made of rock
• Very thin - like the skin of an apple
• Between 8 and 25 miles thick
• Broken into pieces called plates

http//www.ukooa.co.uk
4

• The Earths Layers
• Mantle
• Just beneath the Earths crust
• Solid rock
• Very hot between 1600 and 4000 F
• Some parts soft like melted candy
• Largest layer of earth around 1800 miles thick

http//all3000.narod.ru/
5

• The Earths Layers
• Core
• Center layer of the Earth
• Hottest layer between 4000 and 9000 Fahrenheit
• Outer core is liquid or molten iron
• Inner core is solid iron because of the pressure
• Approximately 2400 miles thick

6

• Moving Crust
• What are plates?
• Rigid blocks of crust and upper mantle rock
• Fit together like a jigsaw puzzle
• 12 major plates
• Float on soft rock of the mantle
• Move a few centimeters each year

Continental Drift Theory
Pangea supercontinent.split apart 200
million years ago
7
Plate Movement / Colliding Plates Places where
plates crash or crunch together are called
convergent boundaries. Plates only move a few
centimeters each year, so collisions are very
slow and last millions of years. Even though
plate collisions take a long time, lots of
interesting things happen. For example, in the
drawing above, an oceanic plate has crashed into
a continental plate. Looking at this drawing of
two plates colliding is like looking at a single
frame in a slow-motion movie of two cars crashing
into each other. Just as the front ends of cars
fold and bend in a collision, so do the "front
ends" of colliding plates. The edge of the
continental plate in the drawing has folded into
a huge mountain range, while the edge of the
oceanic plate has bent downward and dug deep into
the Earth. A trench has formed at the bend.
http//www.cotf.edu/ete/modules/msese/earthsysflr
/plates3.html
http//www.cotf.edu/
8
http//www.cotf.edu/
9
Plate MovementPlates Pulling ApartAs plates
pull apart valleys and volcanoes develop. Where a
divergent boundary crosses the land, the rift
valleys which form are typically 30 to 50
kilometers wide. Examples include the East Africa
rift in Kenya and Ethiopia, and the Rio Grande
rift in New Mexico. Where a divergent boundary
crosses the ocean floor, the rift valley is much
narrower, only a kilometer or less across, and it
runs along the top of a midoceanic ridge.
Examples include the Mid-Atlantic ridge and the
East Pacific Rise. Remember, plate separation is
a slow process.
http//www.cotf.edu
http//www.cotf.edu/ete/modules/msese/earthsysflr/
plates3.html
10

• Mountains
• Highest landforms
• Form when continental plates collide (highest
  mountains) or continental and oceanic plates
  collide.
• Magma (hot soft rock) builds up along the cracks
  and forms long chains of mountains.

http//www.geocraft.com
Mountains like the Himalaya Range of Tibet
resulted from the collision of the continents.
About 50 millions years ago moving tectonic
plates brought the continents of Asia and India
into contact with one another. Such continental
collisions build spectacular mountain
ranges. http//www.geocraft.com
11

• Volcanoes
• Mountains formed by lava ( magma that reaches the
  earths surface) and ash
• Chains of volcanoes form where continental and
  oceanic plates collide.
• Some volcanoes form in the middle of plates over
  hot columns of magma.
• Deep inside Earth, between the molten iron core
  and the thin crust at the surface, there is a
  solid body of rock called the mantle. When rock
  from the mantle melts, moves to the surface
  through the crust, and releases pent-up gases,
  volcanoes erupt. But why does this solid rock
  melt and come to the surface? Extremely high
  temperature and pressure cause the rock to melt
  and become liquid rock or magma. When a large
  body of magma has formed, it rises through the
  denser rock layers toward Earth's surface.

12

• Caused by plates crushing together, scraping past
  each other or bend in along jagged boundaries
• Earthquakes send out seismic waves (ripples like
  form on a pond) and they are measured using an
  instrument called a seismograph.
• The Richter scale measures the strength.
• Many occur along faults (breaks in the plates)
• Click on the URL to see a demonstration of how an
  earthquake occurs. http//www.crustal.ucsb.edu/ics
  /understanding/elastic/rebound.html

13

• What are Fossils?
• Remains or traces of past life found in
  sedimentary rock
• Scientists study fossils to find out about how
  the Earth has changed.

14
Click on this website to see different types of
fossils. http//web.ukonline.co.uk/conker/fossils/
what-is-a-fossil.htm Click on this website to see
how fossils are made. http//web.ukonline.co.uk/co
nker/fossils/how-fossils-were-made.htm Click on
this website for a good site to learn more about
dinosaur fossils. http//www.enchantedlearning.com
/subjects/dinosaurs/dinofossils/
15
Other Sites used in this Presentation The Earths
Layers http//volcano.und.nodak.edu/vwdocs/vwlesso
ns/lessons/Earths_layers/Earths_layers1.html  Land
forms http//www.geocities.com/monte7dco/archipel
ago.htm  Plate Tectonics http//www.enchantedlearn
ing.com/subjects/astronomy/planets/earth/Continent
s.shtml  BrainPop Plate Tectonics and Layers of
the Earth, Fossils http//brainpop.com/  Divergent
, Convergent, Transforming movement http//www.cot
f.edu/ete/modules/msese/earthsysflr/plates1.html  
             
S. Herndon, Fall 2004