Hhh Flashcards
What is the mantle
Semi molten rock that moves very slowly
How big is the earths crust
It is very thin, 20km
What is the crust divided into
Slabs called tectonic plates
What two types of crust are tectonic plates mad of
Continental and oceanic
What is continental crust like
Thicker and less dense
What is oceanic crust like
Thinner and more dense
Why do the plates move
The mantle underneath them is moving
What ia the place where a plate meets called
Boundaries or plate boundaries
What are destructive margins
Where two plates are moving towards each other
Where is an example of a destructive margin
East coast of japan
Explain what happens a destructive margin when a continental plate meets a oceanic plate
The denser oceanic plate is forced down into the mantle and destroyed. This often creates volcanoes and ocean trenches (very deep sections of the ocean floor where the oceanic plate goes down)
Explain what happens at a destructive plate margin when 2 continental plates meet
They smash together but no crust is destroyed
What are constructive margins
Where 2 playes meet moving away from each other. Magma rises from the mantle to fill the gap and cools creating new crust
What is an example of a constructive margins
The mid-atlantic ridge
What are conservative margins
Where 2 plates are moving sideways past each other or are moving in the same direction but at different speeds. Crust isnt created or destroyed
Where is an example of a conservative margin
Along the west coast of usa
How are mountains formed
When techtonic plates collide the sedimentary rocks that have built up between them are folded and forced upwards to form mountains
Where are fold mountains found
At destructive plate margins and places where there used to be destructive margins
Where are some fold mountain
West coast of north america
Why do you get fold mountains
Because a continental plate collides with an oceanic plate or when 2 continental plates collide
How were the andes formed
When a continental plate collided with an oceanic plate
How were the himalayas forme d
When 2 continental plates colide
What are fold mountains like
Very high mountains which are rocky with steep slopes, often with snow and glaciers in the highest bits and lakes in the valleys between the mountains
Why are fold mountains used for farming
They aren’t good for growing crops so they’re used to graze animals. Lower slopes are used to grow crops. Steep slopes are sometimes terraced to make growing crops easier
Why are fold mountains used for hydroelectric power
The steep sided mountains and high lakes make fold mountains ideal for generating power
Why are fold mountains used for mining
They are a major source of metal ores. The steep slopes make access to the mines difficult so zig zag roads have been craved pit on the sides of mountains to reach them
How are the mines in the fold mountains made accessible
The steep slopes make access to the mines difficult so zig zag roads have been craved pit on the sides of mountains to reach them
How are fold mountains used for forestry
Theu are a good environment to grow some tyoes of tree. They’re grown on the steep valley slopes and are used for things like fuel, building materials and to make paper and furniture
How are fold mountains used for tourism
They have spectacular scenery which attracts tourists. In winter people visit for skiing, snowboarding and ice climbing. In summer walkers come to enjoy the scenery. Tunnels have been drilled through some fold mountains to makr straight fast roads. This improves communications for tourists and people who live in the area as its quicker to get to places.
How are volcanoes formed at destructive plate margins
The oceanic plate moves down under the continental plate because its more dense into the mantle where it is melted and destroyed
A pool of magma forms
The magma rises through cracks in the crust called vents
The magma erupts onto the surface( where it is called lava) forming a volcano
How are volcanos formed at constructive margins
The magma rises up into the gap created by the plates moving apart
What are hotspots
Some volcanos form over parts of the mantle that are really hot
What are composite volcanoes
Made off ash and lava thats erupted cooled and hardened into layers
The lava is thick and flows slowly it hardens quickly to form steep sided volcanos
What are shield volcanos
Made up of only lava
The lava is runny it flows quickly and spreads ober a wide area forming a low, flat volcano
What kind of volcano is mount fuji
Composite
What kind of volcano is mauna loa
Shield
What is a shield volcano
Made up of only lava
The lava is thick it flows slowly and hardens quickly, forming a steep sided volcano
What is a dome volcano
Made up of on,y lava
The lava is thick, flows slowly and spreads over a wide area, forming a low flat volcano
What kind of volcano is mount pelée
A dome volcano
How can scientists monitor volcanos to try and predict eruptions and minimise
They monitor the tell tale signs before a volcano erupts, such as tiny earthquakes, escaping gas and changes in shape (bulges in land where magma has built up) these signs mean an eruption is likely
What are super volcanoes
They are volcanos which are much bigger than average volcanos
What are the characteristics of a supervolcano
Flat (unlike normal volcanos, which are mountains)
Cover a large area (much bigger than normal volcanos)
Have a caldera (unlike normal volcanos where theres just a crater at the top)
What is the first step in the formation of a super volcano at a hotspot
Magma rises up through cracks in the crust to form large magma basins below the surface. The pressure of the magma causes a circular bulge on the surface several kilometres wide
What happens after the circular bulge is created in the process of super volcano formation at a hotspot
The bulge eventual cracks, creating vents for lava to escape through. The lava erupts out of the vents causing earthquakes and sending up gigantic plumes of ash and rock
What happens after the vents are created causeing mini earthquakes and sending up ash and rock in the process of super volcano formation at a hotspot
As the magma basin empties the bulge is no longer supported so collapses, spewing up more lava
What happens after the bulge collapses and there is an eruption in the process of super volcano formation at a hotspot
When the eruption is finished there is a big crater called a cladera left where the bulge collapsed. Sometimes these get filled with water to form a large lake
What was the last supervolcano to erupt and when
Lake toba supervolcano, 74000 years ago
What consequenses will occur as a result of a supervolcano eruption
Thousands of cubic km of rock, ask and lava will be spewed out
A thick clous of super heated gas will flow at high speed, killing and burning anything it touches will be destroyed
Ash will soew out and block the sun, causing mini ice ages
The ask will settle over hundreds of square kilometres burying fields and buildings
How do earthquakes occur at destructive plate margins
Tension builds up when one plate gets stuck as its moving down past the other into the mantle
How do earthquakes occur at constructive plate margins
Tension builds along cracks within the plates as they move away from each other
How do earthquakes occur at conservative margins
Tension builds up when plates that are grinding past each other get stuck
How do earthquakes occur once tension has built up
The plates eventually jerk past each other, sending out shock waves which are the earthquake
The vibrations spread from the focus causing more damage
What is the focus
The point in the earth where earthquakes starts
What is the epicentre
Is the point on the earths surface straight above te focus
How often do earthquakes occur
Weak earthquakes are common but strong ones are rare
What are the 2 earthquake measuring scales
The richter and mercalli scale
What doe sthe richter scale measure
The amount of enerfy released called the magnitude
What is magnitude measured with
A seismometer
What is a seismometer
A machine with an arm that moves with the vibrations of the earth
What is meant by the richter scale does not have and upper scale and is logarithmic
An earthquake of magnitude 5 is ten times as powerful as one with magnitude 4
What would a majot earthquake score on thr richter scale
Above 5
What does the mercalli scale measure
The effects of the earthquake
How are the effects of a earthquake measured
Asking eye witnesses for observations of what happened, words or photos
What is the scale of the mercalli scale
Its a scale of 1-12
1 on the mercalli scale
Only detected by instruments
2 mercalli scale
Omly felt by people at rest indoors
3 mercalli scale
Felt by people indoors
4 mercalli scale
Felt by many people dishes and windows rattle
5 mercalli scale
Felt by most people, dishes and windows broken
6 mercqlli scale
Felt by everyone, many objects moved
7 mercalli scale
Some structural damage
8 mercalli scale
Heavy structural damage
9 mercalli scale
Massive structural damage, some buildings destroyed
10 mercalli scale
All buildings damaged, most destroyed
11 mercallu scale
Most buildings destroyed
12 mercalli scale
Total destruction
What is the earths core made of
Solid iron and nickel
