7th Grade Earth Science Notes

Explain what causes the water to move through the cycle?
Water moves from one form to another when heat from the sun is either added or taken away from it. Heat from the sun and gravity from earth are the driving forces of the water cycle.

How does adding or taking heat away from water molecules affect their motion?
Adding heat causes water molecules to move faster, spreads out, and floats upwards.
Taking heat away causes water molecules to slow down, condense, and sinks down.
*note - this is convection *

What is the difference between weathering, erosion, and deposition?
Weathering is the process that breaks down the materia, erosion moves it to a new location, and deposition is where the materials settles.

Why would a mountain get shorter over time?
Weathering caused by wind and water would break down the materials from the top of the mountain, gravity would pull this material down through erosion, and the sediment would settle in a new location most likely somewhere further down the mountain.

What causes volcanoes to form? Describe the process in words or using a diagram.
1. The oceanic plate is more dense, so it sinks beneath the continental plate as they collide.
2. The oceanic plate heats up as it sinks closer to the mantle it melts due to the heat and pressure and becomes magma.
3. The magma then rises through the crust to the surface because it is less dense and contains such high pressure.
4. Volcanoes are formed inland from the subduction zone.

What causes the plates to move? Be specific.
Convection in the mantle causes the plates to move.
The material in the mantle that is closest to the core heats up, the molecules move faster, spread out, and float up to the surface of the mantle.
This material then begins to cool off because it is further away from its heat source and closer to the crust (or surface) of the earth. When it cools, the molecules slow down, start to condense, and sink back towards the core of the earth.
Through this process, the crust of the earth is dragged along with the moving mantle and the plates that make up the crust are moved - slowly - through this continuous convection.

What is the difference between a transform boundary and a divergent boundary?
Transform boundaries involve plates moving alongside each other - in opposite directions or at different speeds while divergent boundaries involve plates moving away from one another and new land being formed between the plates when magma pushes its way up from inside the earth.

Compare the three different ways that the plates converge depending on the type of plates they are. Why do they act differently?
continental - continental: they are the same density so they crush together and build up to mountains
continental - oceanic: oceanic plates are more dense so they sink beneath the continental plate, melt through the process of subduction, and then end up forming a volcano
oceanic- oceanic: both are dense, but the one that is MORE dense ends up sinking beneath the other and forming a volcano