As fresh rock cools at a ridge, what does it record?

• The depth of the water above the ridge
• The fossils trapped in nearby mud
• The direction of Earth field at that time

Wegener could show that the continents had moved. Why did most geologists still reject his idea?

• He could not say what pushed the plates
• He had never seen matching coastlines
• He claimed fossils never crossed oceans

Plates that pull apart at a ridge build new sea floor.

Circle one:   True   False

Hot mantle rock is less dense and cool rock is denser. How does that difference move plates?

• Rising and sinking rock drags the plates along
• Dense rock melts the plates from below
• Light rock freezes the plates in place

The stripes on one side of a ridge mirror the stripes on the other side. What does that pattern show?

• Only one side of the ridge is spreading
• New crust forms at the ridge and moves both ways
• The ridge relocates every million years

Where two plates slide past each other, you should expect a line of tall volcanoes.

Circle one:   True   False

A map shows a deep trench with a line of volcanoes beside it. What is happening at that boundary?

• Two plates are pulling apart
• One plate is diving under another
• Two plates are sliding sideways

Mara says matching fossils and fitting coasts settled the debate at once. What is her mistake?

• Fossils have never matched across an ocean
• Coastlines only fit on modern drawn maps
• Even strong clues failed with no driving force