What key features have emerged through the examination of the map ...

[APUS57]

What key features have emerged through the examination of the map of Earth's magnetic field?
 
  What will be an ideal response?

Question 2

How does convection work?
 
  What will be an ideal response?

[heinisk01]

Answer to Question 1

Answer: 1. The pattern of Earth's magnetic field very closely, but not exactly, resembles the field of a bar magnet. The analogy works only if the hypothetical magnet producing Earth's field is located deep in the interior. This observation, made in the nineteenth century, led to the conclusion that Earth's magnetism originates deep within Earth and not at the surface or somewhere in space.
2. The north magnetic pole, where the force lines go into Earth, and south magnetic pole, where the force lines emerge, do not coincide exactly with the geographic north and south poles. Currently, the angular distance between the magnetic and geographic poles is about 18 degrees.

Answer to Question 2

Answer: Convection is the simultaneous movement (transfer) of matter and heat, whereas conduction transfers only heat from hot to cold regions. Convection happens when gravity forces that cause motion are greater than viscosity forces that resist motion; in other circumstances, heat transfers by conduction. Thermal convection originates from density contrasts between got and cold materials. Higher density contrast, which favors convection, is present in materials that have low heat conductivity and large expansion when heated. Calculations show that convection should occur in the whole mantle and in the outer core, but not within the lithosphere or inner core. Convection in the outer core results from density variations caused by compositional differences, rather than by temperature differences that cause mantle convection.