Given a scientific passage and an answer, generate a question for the given answer.

Example Input: Passage: A cross section of earthquake epicenters. The depth outlines the subducting plate. There are shallow, intermediate, and deep earthquakes. Answer: earthquake
Example Output: Subducting plate and epicenter are terms related to what phenomenon?

Example Input: Passage: Asexual reproduction involves just one parent. It produces offspring that are genetically identical to the parent. Methods of asexual reproduction include binary fission, fragmentation, and budding. Answer: asexual
Example Output: What type of reproduction only involves one parent?

Example Input: Passage: But ice ages also occurred many times in the past. An ice age is a period when temperatures are cooler than normal. This causes glaciers to spread to lower latitudes. Scientists think that ice ages occurred at least six times over the last billion years alone. How do scientists learn about Earth's past climates?. Answer: ice age
Example Output:
What is the term for a period when temperatures are cooler than normal causing glaciers to spread to lower latitudes?