In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.
Q: One type of motion at this location is called Slichter modes, and the existence of this location was first proposed by Inge Lehmann. The rotation of this region and its interaction with a region above it give rise to the dynamo theory, the idea that this region is responsible for the Earth's magnetic field, and this region is theorized to be solid despite its high temperature, because of the high pressure here. For 10 points, identify this deepest region of the Earth, located within a similarly-named ""outer"" region.
A:
Science