geography exam Flashcards
stuff i didnt know in my pre (23 cards)
Explain how convection currents occur
The earths core heats the magma from the mantle, causing it to rise slowly upwards towards the crust. As the magma rises, it then begins to cool. This cooling results in the magma becoming heavier and sinking back down to the core. The cycle then repeats causing circular motions of magma. (convection currents).
What heats the magma from the mantle?
The earth’s core
What happens to magma as it rises towards the crust?
It begins to cool
What is the result of magma cooling?
It becomes heavier and sinks back down to the core
What do the circular motions of magma caused by heating and cooling represent?
Convection currents
Fill in the blank: The cycle of heating and cooling of magma causes _______ motions.
circular
True or False: The cooling of magma leads to it rising again.
False
Why do Volcanoes occur in Iceland?
Volcanoes occur in Iceland because it is situated on a separating plate boundary. As convection currents cause the plates to move, magma rises out of the ground. Over time, this magma hardens and builds up to form volcanoes.
Why do volcanoes occur in Iceland?
Iceland is situated on a separating plate boundary.
What causes the movement of tectonic plates?
Convection currents.
What happens to magma as it rises out of the ground?
It hardens and builds up to form volcanoes.
How is limestone formed?
Rocks on the surface of the earth are worn down over time. Some broken pieces are dropped in layers on the sea floor. Here, they become pressed and cemented together, mixing with dead sea creatures to form sedimentary rocks. (limestone and sandstone).
What happens to rocks on the surface of the earth over time?
They are worn down
What occurs to broken pieces of rocks after they are worn down?
They are dropped in layers on the sea floor
What process occurs to broken pieces of rocks on the sea floor?
They become pressed and cemented together
What do broken pieces of rocks mix with on the sea floor to form sedimentary rocks?
Dead sea creatures
What types of sedimentary rocks are formed from the process described?
Limestone and sandstone
How can people use rivers (other than for water supply)?
People can use rivers as transportation. They can use boats on rivers to carry goods from one city to another. They can use ferries to transport people from one place to another. They can also transport themselves when fishing from one spot to another in a river.
Explain how overgrazing contributes to desertification.
When there is too many animals grazing on an area, they eat young plants and roots. This means they wont grow. This contributes to turning the land into desert by reducing the amount of organic matter in the soil, drying out and depleting fertility in the soil.
Describe how planting trees can reduce desertification.
Roots of trees act as an anchor to soil. This reduces erosion. Planting trees can reduce desertification because trees/leaves add humus to soil, which increases soil fertility, allowing for crops to thrive on that land. Shade from trees can also reduce evaporation, meaning crops can retain more water/liquids.
How is humus formed?
Humus is a black or dark brown sticky substance rich in nutrients. it is formed from the broken down remains of dead plants and animals. It is mixed into the soil by organisms to increase soil fertility and help bind the soil.
What role do organisms play in relation to humus?
They mix it into the soil to increase soil fertility and help bind the soil
True or False: Humus is only found in dry soils.
False
