The Dynamic Earth Flashcards
Internal structure of the earth
THE INNER CORE:
- mostly iron and is solid
- about 1,300 kilometres wide
- temperatures can reach up to 7000º C.
THE OUTER CORE:
- made up of molten iron and nickel
- around 2,250 kilometres thick
- temperatures mostly between 4000º C and 6000º C.
THE MANTLE:
- about 2,900 kilometres wide
- temperatures between 500º C and 2000º C
- made up of partially molten rock and magma
THE CRUST (OR LITHOSPHERE):
- mostly solid rock, which is very strong and rigid
- It includes landforms, rocks and soil.
- varies in thickness, small as 5km to as big as 70km
Which scientist developed the Theory of Continental Drift?
Explain his theory.
Alfred Wegner (German meterologist) developed the theory
- theory is about how continents shift position on the Earth’s surface
- originally one ‘supercontinent’ referred to as Pangea
- Eventually Pangea broke up into smaller parts and formed the seven continents
Why didn’t fellow scientists believe Wegner’s theory?
- a lack of mechanism
- His assumptions were easily challenged
- didn’t have a clear explanation of how continental drift could have occurred
What evidence is ther that Continental Drift occured?
The evidence was the discovery of fossils of the same land animals on different continents.
Continetal crust
- the plates that make up the continents/land
- generally between 30 km and 70 km thick
Oceanic crust
- plates beneath the ocean
- a lot denser and thinner than continental crust
- average thickness is about 6 km.
What causes plates to converge?
Converging plates are caused when two plates push against each other
What do we call the boundaries between converging plates?
- They are called destructive plate boundaries
- This is because solid ocean crust melts into the mantle
Example of a constructive plate boundary
The Eurasian Plate
Example of a destructive plate boundary
The Pacific plate
An example where ocean ridges are formed.
Ocean ridges are formed by convection currents rising in the mantle beneath the oceanic crust and creating magma where two tectonic plates meet at a divergent boundary.
Example: Mid-Atlantic ridge
An example where subduction occurs.
Subduction occurs when one tectonic plate (at a convergent boundary) moves under another tectonic plate and sinks into the mantle. Areas where this occurs are eknown as subduction zones.
Example: the “ring of fire”
FOLDING ROCK - explain and give an example
Occurs when the forces beneath the Earth are so powerful that layers of rock bend and crumple without breaking.
Example: Australia’s Great Dividing Range
NORMAL FAULT - explain and give an example
- Occurs when the hanging wall block moves downwards while the footwall block moves upwards
- It is the result of the Earth’s crust spreading apart.
Example: The Long Point–Eureka Heights fault system
REVERSE FAULT - explain and give an example
Occur when the hanging wall block moves up while the footwall block moves down
Example: The Sierra Madre fault zone of southern California
SLIP FAULT - explain and give an example
Occurs when blocks of crust slide horizontally past each other
Example: The San Andreas Fault in California
RIFT VALLEYS - explain and give an example
Occurs between two sunken blocks of crust, where there is a block that has been pushed upwards by the forces below
Example: the Gulf of California Rift Zone.
What causes earthquakes?
Earthquakes occur when the Earth’s crust shifts below the surface.
What is the epicentre?
The epicentre is the point directly above the focus (the focus is the point below the surface where the movement begins).
What scale is used to measure the size of an earthquake?
- The Richter scale
- An earthquake is measured by the amount of energy it releases
List the three types of seismic waves
P-WAVES (primary waves):
- compression waves
- fastest of all the Seismic waves
- travel through the body of the Earth the same way that sound waves travel through air
S-WAVES (secondary waves):
- The second set of waves detected after P-waves
- They are transverse waves
- travel through the body of the Earth
L-WAVES:
- These are surface waves
- travel around the Earth
- They are the slowest Seismic waves
- they are responsible for causing the majority of an earthquake’s catastrophic power
How are tsunami’s formed?
- First, the rapid movement of the ocean floor (from an earthquake) upsets a column of water.
- This creates enormous waves that travel through the ocean at speeds up to 900 km/h
- As the waves approach land, the water gets shallower which forces the waves’ energy to compress into a smaller space
- Causes the waves to gain height (up to 30 metres high) and slow down
- The wave then breaks at land and causes mass destruction.
Explain lava
When magma reaches the surface and expels from the mouth of the volcano, it becomes lava.
Explain magma
Magma is red-hot molten rock that is found underneath the Earth’s crust.
