One of the pieces of evidence for evolution that Charles Darwin collected on his travels aboard the HMS Beagle was the observation of fossils of extinct animals and similar but noticeably different current species. Giant ground sloth fossils were very similar in shape to the bones of sloths that inhabited the regions of South America he was exploring. The main difference was the size, the ground sloth fossils were significantly larger than the bones of the sloths he captured alive. What was a conclusion that Darwin was able to develop based on this piece of evidence?

1. seamount a raised footwall block between normal fault creates this 2. syncline break between rocks where a hanging wall rises relative to a footwall 3. hot spring on rolling hills, this a dip between hills 4. volcanic neck created when a block with hanging walls slips down between normal faults 5. caldera underwater volcano that never reaches above sea level 6. horst natural hot water on earth's surface containing many minerals 7. graben underwater volcano whose top is eroded flat by waves 8. crater less than a mile in diameter; looks like a bowl at the top of a volcano 9. guyot magma that filled the central vent that remains after the volcano has eroded 10. reverse fault over 1 mile in diameter; looks like a bowl over a volcano