Restless Earth Knowledge Flashcards
What is the thicker type of crust
Continental
Which Type is the older type of Crust at 4.3 billion years old
Continental crust
Which way do the plates move at a destructive boundary
Towards each other
In which boundary do the plates move away from each other
Constructive
Conservative margins move…
Side to side of each other
Name the features that can occur at a destructive boundary
Composite volcanoes
Earthquakes
Fold mountains
Ocean trenches
Constructive boundries create…
Shield volcanoes
Volcanic islands
Describe what happens in a subduction zone
The lighter continental plate stays on top whilst the heavier oceanic crust is pushed down where it melts
Describe briefly the three stages in the formation of a fold mountain
Sediment forms a thick layer in a geosyncline
The sediments have great pressure in them and solidify
The plates move towards each other forcing the rock up
What is an anticline
The peak of a mountain
Why aren’t ocean trenches any use to humans
To deep to harvest any products from
How are earthquakes measured in:
A) the Richter scale
B) the mercali scale
a) seismographs
B) human judgement
What does the Richter scale measure and how
The magnitude and in a logarithmic scale from 1-10
What numerical system is used by the mercali scale
Roman numerals
Describe three physical factors that increase the impact of an earthquake
High magnitude
Shallow focus
Weak foundations eg sand and clay
Describe four human factors that decrease the impact of an earthquake
Low population density
Non residential area
Good housing regulations
Frequent drills
Describe a composite volcano in five points
Steep Narrow base Viscous lava Made of lava + ash Irregular eruptions
Describe a shield volcano in five points
Gentle slopes Wide base Runny lava Only made up of lava Frequent but inexplosive eruptions
How many times bigger is a supervolcanos eruption than a regular volcano
1000 times bigger
What two global effect would a super volcano eruption have on earth
Global dimming
Global cooling
Define focus
The underground centre of the earthquake
“The point directly above the focus”‘is a definition of what
The epicentre
How do shockwaves move
They radiate out from the focus in all directions
Name the four stage process in which a tsunami is caused
Two plates get stuck the. Lose their tension suddenly
An underwater earthquake occurs
Sea bulges up
Waves move towards land
Which is the denser type of crust?
Oceanic
Describe oceanic crust in 4 points
Newer
Denser
Sink able
Can be renewed
Describe continental crust in 4 points
Older
Less dense
Can’t sink
Cannot be renewed or destroyed
Where are constructive margins most common
Under the ocean
What occurs at constructive plate boundaries
Shield volcanoes
Small earthquakes
Formation of new land
What type of manga comes from constructive margins
Runny lava
At a destructive margin which plate subducts under which plate
Oceanic goes under the continental
What happens to the oceanic crust in the subduction
It melts and forms magma
Why forms a destructive plate boundaries
Ocean trenches
Composite volcanoes
Fold mountains
Earthquakes
What is a collision margin
A destructive boundary In which both plates are made of continental
What forms at collision margins and give an example
Fold mountains eg Himalayas
In a conservative plate boundry describe the movements of each plate
Both plates are going overall in the same direction. One plate may be going faster and so they rub past each other
How are earthquakes distributed
In linear patterns along plate boundaries
How are volcanoes distributed
In linear patterns along plate boundaries and hot spots
Where do over half the worlds earthquakes occur
Pacific ring of fire
What is the first stage I the formation of a fold mountain
Sediment settles under the ocean in a geosyncline
What are the second and third steps of the fold mountain formation
The sediment forms sedimentary rock then the destructive plates push it together forcing the rock up
How deep are ocean trenches
5000-10,000 meters
What is the Benioff zone
Where earthquakes occur in a destructive boundry
Why is the lava coming from shield volcanoes more runny
Because it has a low silica content
Shield volcanoes are made only from…
Lava
Shield volcanoes erupt …
Frequent
How are composite volcanoes formed
In the subduction zone of a destructive boundry a pool of magma forms, pressure pushes this up through cracks. Thus causing an eruption, the lava is high silica and so solidifies quickly, over eruptions it builds up
Composite volcanoes are formed by
Ash and lava
What are lahars
Mudflows formed by the mixing of water and volcanic ash
Why do people live near volcanoes
Fertile soils
Tourist attractions (hot springs geysers)
Geothermal power
Valuable minerals (sulphur, borax, pumice)
What minerals can be found in volcanoes
Diamonds, borax, pumice
What are the signs a volcano eruption is going to happen
Small earthquake
Steam and gases out of the crater
The crater bulges
The temperature changes
What is a tiltmeter
A bit of kit to measure slight changes in a volcanoes profile
What is the main way volcanoes can be predicted in the long run
Historical records
Where d super volcanoes occur at
Hot spots
What is the name for the large depression in which a super volcano is formed
A caldera
After the eruption what happens to the user volcanoe
It collapses into the caldera
Where is the focus
Exactly at the origin of the earthquake (underground)
Where is the epicentre of an earthquake
The point directly above the focus on the ground
Why is prediction hard for earthquakes
It’s very hard to tell when it’s going to happen
What do the Chinese and Japanese do to predict earthquakes
Monitor animal behaviour
Why are the primary and secondary waves less powerful
Because they are underground
What physical factors decrease the damage of an earthquake
Low magnitude
Deep focus
What human factors increase damage done by an earthquake
Population density
Residential area
Self built housing
Lack of response
How can houses be protected from earthquakes
Steel frames that move with earthquake
Fire resistant materials
Well built foundations
Shock absorbers
What starts a tsunami
Earthquakes at sea
Why do the waves of tsunami get bigger towards the coast
Because they slow down
Low silica content lava is Also known as what and is found where
Basic lava and in shield volcanoes
High silica content is also know as what and is found where
Acidic lava and is found at composite volcanoes
