What was the strongest evidence that the continents were once joined together?
AThe continents are all the same shape
BMatching coastline shapes, identical fossils on separate continents, and matching rock formations across ocean basins
CAncient maps showed the continents connected
DSailors reported seeing the continents move
Wegener compiled multiple independent lines of evidence: the jigsaw fit of continents (especially South America and Africa), identical fossils of land animals found on continents now separated by thousands of kilometers of ocean, matching rock types and mountain chains that align when continents are reassembled, and glacial evidence in currently tropical locations.
Question 2 Short Answer
Why was Wegener's continental drift hypothesis rejected by most scientists for decades?
Think about your answer, then reveal below.
Model answer: Wegener could describe the evidence that continents had moved but could not explain what force was powerful enough to move entire continents. Without a plausible mechanism, most scientists found his idea unconvincing, even though his evidence was strong.
This changed in the 1960s when scientists discovered seafloor spreading and mapped the system of mid-ocean ridges. This provided the mechanism Wegener was missing: the continents are carried on tectonic plates that are pushed and pulled by forces in the mantle. Wegener's observations were vindicated, but the explanation was different from what he had proposed.
Question 3 True / False
Continents move at a rate of several meters per year.
TTrue
FFalse
Answer: False
Continents typically move only a few centimeters per year — about the speed fingernails grow. This is why the movement is undetectable without precise instruments. Over millions of years, however, a few centimeters per year adds up to thousands of kilometers.