Complete question: (Note: I failed to find the exact same question with its options, so I included many possible statements about convection)
The mantle is the layer in which convection occurs causing the crust to move. Which statement below best describes the convection currents in Earth's mantle?
- They transfer potential energy away from Earth's core toward its crust.
- They transfer thermal energy away from Earth's core toward its crust.
- They transfer chemical and thermal energy in a circular pattern.
- They transfer chemical and potential energy in a circular pattern.
- Convection occurs in solids.
- Convection occurs in liquids and gases.
- Convection transfers thermal energy.
- Convection transfers potential energy.
- Convection occurs until all of the fluid is at the same temperature.
- Convection occurs only one time, no matter the temperature.
- thermal energy is transferred by physical contact
- thermal energy is transferred by electromagnetic waves
- thermal energy is transferred by movement in fluids
- thermal energy is transferred by mechanical waves
- the motion in a convection current horizontal
- the motion in a convection current vertical
- the motion in a convection current linear
- the motion in a convection current circular
Answer:
- They transfer thermal energy away from Earth's core toward its crust.
- Convection occurs in liquids and gases. Convection transfers thermal energy. Convection occurs until all of the fluid is at the same temperature.
- Thermal energy is transferred by movement in fluids.
- The motion in a convection current circular.
Step-by-step explanation:
The convection currents are the result of heating by temperature gradients. Differences in temperature and density produce these currents. Warm materials are lighter and can ascend, while cold materials are heavier and denser, so they tend to descend. These materials movements create a circular motion pattern known as convective currents. They occur in the atmosphere, in the water, and the earth´s mantle.
In the last case, while the hot mantle emerges from the deepest areas, the cold mantle sinks, creating a circular convection current. These play an important role in fluids circulation and might be responsible for the movements of the lithospheric plates that are over the mantle. The temperature in the oceanic lithospheric plates is much inferior to the mantle´s temperature, so the lithospheric pieces sink, creating a descendent current.
Near the terrestrial core, the temperature might reach up to 3,500ºC, and solid materials in these areas melt and fuse. When fusing, materials lose density, becoming lighter and ascending again to the surface, creating the ascending currents. The currents of ascending materials are known as thermal feathers or plumes.