2. Convection Currents

Question One: Where does the heat come from that drives this convection current in the mantle?

The heat driving the convection current in the mantle comes from the extreme temperature in the earth's core, and the heat from the mantle itself.

Question Two: Where is the temperature of the mantle material greater, at point A or point B? Explain why.

Point A, as the closer to the centre of the earth, the higher the temperature. Also this point is where the fluid in the convection begins to heat up, before rising to point B where it cools.

Question Three: Where is the density of the material greater, at point B or point C? Explain why.

Point C, as the material passing through this point would have been at the top of the mantle for longer than the material at point C (which would have just risen). The material would then have had longer time to cool down at the lower temperature part of the mantle, and would become denser and a lower temperature.

Question Four: What causes the convection cell to turn to the left at point B?

Point B is in between two convections, and is just below a ridge. This causes the cell to turn left because the flow of fluid hits the bottom of the crust/lithosphere, and is forced to turn left.

Question Five: What happens to the temperature and density of the material between points B and C?

As the fluid flows between these points, it adjusts to the lower temperature at the top of the mantle and cools down. This slows the particles, causing them to move closer together, increasing the density.

Question Six: What force causes the convection cell to turn down at point C?

Point C is where a trench in the crust lies, so the convection current is forced to turn. Since the fluid at point C would have been flowing at the top of the convection current for a longer time than the fluid at point B, it has had more time to cooler down and increase in density, causing it to fall back towards the core of the earth.

Question Seven: What happens to the temperature and density of the material between points D and A?

At point D, the fluid in the convection current has just come from the top of the convection, so it would be quite dense. It would then flow between points D and A, and would adjust to the higher temperature being closer to the earth's core. This would cause the particles to spread apart more with the added heat and the fluid would decrease in density.

Question Eight: What causes the convection cell to turn up at point A?

At point A, the two convection currents hit each other, pushing the fluid upwards. The to currents don't merge because they are both going in different directions, and by the time the fluid in the currents reach this point, they have heated up enough to be less dense than the fluid they are surrounded with, so the rise to the top of current below the crust.

Question Nine: How do you think this convection cell might affect the crust material above it

The convection cell is going anti clockwise, so the top of the current would be gradually pushing the crust above it the same way. This would most likely cause a subduction in the trench above point B, as the crust would be pushed to the left, cause it to collide with the other plate and dive under.

LESSON #1: GEOLOGY: TECTONIC LANDFORMS

1. NOTES PDF -Continental Drift to Plate Tectonics

Open: From Continental Drift to Plate Tectonics (PPT)

- Use the FITB Ws to complete your notes

2) INTERACTIVE SITE:

Go HERE and answer