What is continental drift theory?

• A. The continents are fixed in place
• B. The continents are increasing in size
• C. The continents were once joined and then slowly drifted apart
• D. The Earth is flat

Answer: (C)

Continental drift theory explains how Earth's continents have moved over long geological timescales. The correct idea is that the continents were once joined together in a single landmass and have slowly drifted apart to their present positions. This fits the evidence from the fit of coastlines, the matching fossils of plants and animals across now-separated continents, and the alignment of rock types and mountain belts on different continents. It’s also supported by clues from ancient climates, such as glacial deposits in now-tropical areas, which make sense only if continents were in different locations in the past.

The mechanism behind this movement is plate tectonics: the Earth's lithosphere is cracked into plates that float on the semi-fluid mantle and move due to convection currents. New crust forms at mid-ocean ridges and is recycled at subduction zones, driving the movement of continents over time.

Options suggesting fixed continents, increasing in size, or a flat Earth don’t fit the evidence and the observed geological and paleontological records.