(Q021) During the Pleistocene Ice Age,Group of answer choicescontinental glaciers in the northern hemisphere advanced and retreated only once.sea level rose because water was tied up as ice.the continental shelf west of Alaska was exposed and allowed migration of animals and people from Asia to North America.continental glaciers covered all of North America.

During the Pleistocene Ice Age,Group of answer choicesthe southern boundary of the North American tundra moved 20° of latitude northward.pluvial lakes dried up in Utah and Nevada, while increased rainfall farther south caused equatorial rainforests to flourish.CaCO3 shells in the world's oceans recorded a low ratio of O18 to O16.mammoths, mastodons, woolly rhinos, saber-toothed cats, and giant cave bears inhabited North America.

(Q020) Recent studies of ice agesGroup of answer choicesreveal fewer ice ages and less complexity than was originally thought.have identified paleosols that form during glacial periods.have identified glacial events by analyzing oxygen-isotope ratios in marine sediments.suggest that the entire Earth was covered by glacial ice in the Pleistocene.

What do geologists think happened as the last ice age ended?A.A mass extinction occurred.B.Sea levels rose over 300 feet.C.Dense forests grew for the first time.D.Glaciers advanced worldwide.

The __________ suggests that during the Ice Age, an ice-free corridor opened between Siberia and North America around 12,600 years ago.Group of answer choicesKelp Highway HypothesisLake Mungo HypothesisCoastal Highway HypothesisBeringia Land Bridge hypothesis

A theory explaining ice ages must also address the fact that during the Pleistocene IceAge (2.6 million to 11,700 years ago) several intervals of glacial expansion separated by warmerinterglacial periods occurred. At least four major episodes of glaciation have been recognized inNorth America, and six or seven glacial advances and retreats occurred in Europe. Theseintermediate-term climatic events took place on timescales of tens to hundreds of thousands ofyears. The cyclic nature of this most recent episode of glaciation (i.e., during the Pleistocene) haslong presented a problem in formulating a comprehensive theory of climatic change.2. The word “comprehensive ”in the passage in meaning toA: complete B: convincing C: well supported D: widely accepted3. According to paragraph 3, which of the following is a fact that theories about ice ageshave had difficulty explaining?A: The Pleistocene was separated from the previous ice age by a long interval of mild climate.B: During the Pleistocene Ice Age, glacial advances and retreats alternated in a cyclic pattern.C: There have been notably fewer episodes of glaciation in North America than in Europe.D: The Pleistocene Ice Age gave way to milder climate about 10,000 years ago.