Dynamic Planet I-3 AYR Answers

Question 1 What are the conditions that cause convection cells in a fluid? What are the conditions that cause convection cells in a fluid?

Convection occurs when a fluid is heated from below and cooled from above. Heating the fluid makes it expand slightly, which makes it less dense, so it rises. When the heated fluid cools at the top of the cell (usually when it approaches or reaches the surface), it contracts or shrinks, becomes more dense, and sinks. Convection occurs when a fluid is heated from below and cooled from above. Heating the fluid makes it expand slightly, which makes it less dense, so it rises. When the heated fluid cools at the top of the cell (usually when it approaches or reaches the surface), it contracts or shrinks, becomes more dense, and sinks.

Question 2 How can the mantle convect if it is a solid? How can the mantle convect if it is a solid?

The mantle can convect because the mantle rock is just hot enough and under enough pressure to slowly deform. In effect, the mantle rock acts like a liquid on a very long time scale. The mantle can convect because the mantle rock is just hot enough and under enough pressure to slowly deform. In effect, the mantle rock acts like a liquid on a very long time scale.

Question 3 What is the typical speed of mantle convection? What is the typical speed of mantle convection?

The typical speed of mantle convection is a few centimeters per year. The typical speed of mantle convection is a few centimeters per year.

Question 4 What is the reason for volcanic activity along mid-ocean ridges? What is the reason for volcanic activity along mid-ocean ridges?

Hot mantle rock rises in convection cells. As it approaches the surface, some of it melts to form magma, and the magma forms volcanoes on the sea floor. Hot mantle rock rises in convection cells. As it approaches the surface, some of it melts to form magma, and the magma forms volcanoes on the sea floor.

Question 5 What kinds of forces drive sea-floor spreading? What kinds of forces drive sea-floor spreading?

The melting of mantle rock at the top of a rising convection cell provides a supply of magma that forces the lithosphere apart at mid-ocean ridges. The downhill slope of the ridge away from the crest of the ridge adds to the forces that move the new ocean crust away from the ridge. The melting of mantle rock at the top of a rising convection cell provides a supply of magma that forces the lithosphere apart at mid-ocean ridges. The downhill slope of the ridge away from the crest of the ridge adds to the forces that move the new ocean crust away from the ridge.