The Restless Earth Flashcards
Why so plates move?
The mantel is semi-molten. This means that certain areas get heated up, move to the side and fall.
Describe the structure of the earth.
Crust 6-10 Km
Mantel. Thick layer of jam consistency. Ranges from 5,000C-1,300C
Outer core. Liquid made of iron.
Inner core. Solid iron can reach 5,500C. Normally 3,700C
Explain a divergent plate boundary.
Also called a constructive boundary.
Two plates move apart and magma goes up between the two. This can cool and form new land. This is how Iceland formed when the North American plate and the Eurasia plate moved apart. This also formed the mid Atlantic ridge.
What are the differences between continental and oceanic plates?
Continental plates are thicker and lighter.Oceanic plates are thinner and more dense.
What are the places where plates meet called?
Boundaries or plate margins.
What are the three types of plate margins?
Destructive, constructive or divergent and conservative.
Explain a destructive plate margin.
It happens when two plates are moving towards each other like along the coast of Japan.
When the denser oceanic plate meets the continental plate, the denser plate is sub ducted into the mantel and is melted. This can create volcanoes and ocean trenches.
What happens when two continental plates move towards each other?
They smash together but none of it is destroyed. Fold mountains can form here.
Explain a conservative plate margin.
It is when two plates are moving sideways past each other or moving in the same direction but at different speeds. This can cause earthquakes when one of the plates, suddenly jerks forward. This happens along the west coast of the USA.
How do fold mountains form?
They form when two plates move together. When the plates aren’t moving, sedimentary rock will form in the depression between the two. This rock will form when a river carries sediment and deposits it into the depression. This will form sedimentary rock after millions of years. The depression where the rock forms is called a geosyncline.
When the plates move together the rock will get forced upwards and this will happen in a series of folds called anticlines and synclines.
What are anticlines?
Folds up in a fold mountain.
What are synclines?
Down falls in a fold mountain.
At what type of plate boundary do fold mountains form?
Destructive plate boundaries like in the west coast of North America.
What are the characteristics of fold mountains?
They are very high, with very rocky and steep slopes. There’s often snow and glaciers in the highest areas and lakes in the valleys between the mountains
How do humans use fold mountains for farming?
Higher mountain slopes can’t be used for crops so they are used for animals like goats and cows. Lower slopes are used to grow crops but the steeper ones can be terraced to make growing crops easier.
How do humans use fold mountains for hydro-electric power?
Steep sided mountains and high lakes make fold mountains good for hydroelectric power.
How do humans use fold mountains for mining?
Fold mountains are a major source for metal ores. Steep slopes make access to the mines difficult so zig-zag roads have been caved on the sides.
How do humans use fold mountains for forestry?
They are good for growing certain types of trees. They’re grown on the steep valley slops and the wood is used for fuel, paper and building materials.
How do humans use fold mountains for tourism?
They have nice views which attract tourists. In winter, people do sports like skiing, snowboarding and ice climbing.
In summer, walkers enjoy the scenery. Tunnels have been drilled through some of the mountains to improve access.
Where are the alps? how did they form and how many people live there?
Central Europe. It stretches across Austria, France, Germany, Italy, Liechtenstein, Slovenia and Switzerland.
They formed 30 million years ago by a collision between the African and European plates. 12 million people live there.
How are the alps used for farming?
The steep upland areas are used to farm goats, which provides milk, cheese and meat.
Sunnier slopes have been terraced to plant vineyards like in Lavaux Switzerland.
In winter the animals are returned to the valley where they are kept in sheds. The farming type is dairy farming using a system called transhumance. (Seasonal movement of the animals)
Cable cars and pipes have been used to move milk around.
How are the alps used for hydro-electric power?
Narrow valleys are dammed to generate power like in the Berne area. 60% of electrify in Switzerland comes form hydroelectric power.
The power is used locally to power homes and businesses. Power is also exported to over towns, cities and other nations.
How are the alps used for tourism?
100 million tourists visit the alps every year.
70% of the tourists visit the steep, snow covered mountains in winter for skiing and snow boarding. In the summer tourists visit for walking, mountain biking and climbing.
New villages have been built to cater for the tourists like Tignes.
How are the alps used for mining?
Salt, iron ore, gold, silver and copper were mined in the alps, but the mining has declined dramatically due to cheaper foreign sources.
How are the alps used for forestry?
Scots pines are planted all over the alps because it’s more resilient against goats. Trees are logged and sold to make furniture.
How have people adapted to conditions in the alps?
The soil is poor so animals are grazed in high areas.
Steep relief. Goats are farmed on the steep sides as they are adapted to it. Trees have been planted to protect against avalanches and rock slides.
How do volcanoes form at destructive plate boundaries?
At destructive plate boundaries when the oceanic plate goes under. It will melt in the mantle, forming a pool of magma. This will rise through cracks in the crust called vents. The magma erupts onto the surface.
Other than destructive plate boundaries where do volcanoes form?
At constructive margins where magma rises up in the gap between tow plates or where the mantel is very hot (hotspots) like in Hawaii.
What are the three types of volcanoes?
Composite, shield and dome.
Explain composite volcanoes.
Made of ash and cooled, erupted lava. This means many layers. The lava is usually thick and flows slowly when it gets out. This hardens quickly to form steep sided volcanos. This type emits ash as well e.g. Mount Fuji
Explain shield volcanoes.
Made of only lave. The leaves runny. It flows quickly and spreads over a wide area, forming a low flat volcano e.g. Mauna Loa
Explain dome volcanoes.
Made of lave only. The leaves thick. It flows slowly and hardens quickly, forming a steep-sided volcano e.g. Mount Pelée
