Which pieces of evidence support plate tectonics (paleomagnetism, seafloor spreading, and hot spots)?

• A. Fossil distribution across continents only
• B. Magnetic stripes symmetric around ridges, seafloor spreading, hot-spot trails
• C. Glacial till lines in deserts
• D. Seafloor subduction zones alone

Answer: (B)

The main idea is that Earth’s lithosphere is made of moving plates, and several independent lines of evidence converge to support that. Paleomagnetism shows magnetic stripes on the ocean floor that are symmetric about mid‑ocean ridges. As new rock cools at a ridge, it records Earth's magnetic field; reversals create a pattern of normal and reversed polarity that mirrors on both sides, demonstrating that new crust forms at ridges and spreads outward. Seafloor spreading is the process that generates that outward motion, linking the symmetrical stripes directly to the creation and movement of oceanic crust. Hot spots add another crucial piece: as a plate moves over a relatively fixed mantle plume, a chain of volcanoes forms and ages progressively along the track, revealing the direction and rate of plate motion over time.

Choosing the option that explicitly includes magnetic stripes, seafloor spreading, and hot-spot trails best captures the combined evidence from paleomagnetism, the spreading process, and hotspot-driven tectonics. Other statements either reference evidence that doesn’t directly show plate motion (like fossil distributions or glacial traces) or point to one aspect (such as subduction) without the complementary clues that tie everything together.