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Quarternary Period consists of two unequal epochs:

the Pleistocene Epoch, from 1.6 million years ago to 10,000 years ago, and the Holocene Epoch, from 10,000 years ago to the present

in addition to glaciation, the Pleistocene was also a time of tectonic unrest during which what was common

folding, faulting, uplifts, and volcanism

during the Pleistocene Epoch, glacier covered about

30% of the land surface

how many warm-cold Pleistocene climatic cycles are recognized

20 warm-cold Pleistocene climatic cycles

how are the Pleistocene climatic cycles recognized

from paleontologic and oxygen isotope data derived from deep-sea cores

how did glaciation occur in North America

several intervals of widespread glaciation, separated by interglacial periods

were also affected by widespread glaciation

other Northern Hemisphere continents

areas far beyond the ice were affected by Pleistocene glaciation:

climate belts were compressed toward the equator, large pluvial lakes existed in what are now arid regions, and sea level was as much as 130 m lower than at presetn

loading of the Earth's crust by Pleistocene glaciers caused

isostatic subsidence

when the glaciers disapperared

isostatic rebound began and still continues in some areas

probably occur as a consequence of the changing positions of tectonic plates

major glacial intervals separated by tens or hundreds of millions of years

changing positions of tectonic plates cause changes in

oceanic and atmospheric circulation patterns

theory widely accepted as the explanation for glacial-interglacial intervals

Milankovitch

reason for short-term climatic changes, such as the Little Ice Age are

not understood

two proposed causes for short-term climatic changes are

changes in the amount of solar energy recieved by the Earth and volcanism

mineral resources of the Quaternary are mainly

sand and gravel along with some evaporite minerals such as borax

glacial stage

time of extensive glaciation. at least four of these are recognized in North America, and six or seven are recognized in Europe

Holocene Epoch

last of two epochs comrising the Quarternary Period. began 10,000 years ago

interglacial stage

time between glacial stages when glaciers cover much less area and global temperatures are warmer than during a glacial stage

isostasy

theoretical concept of the Earth's crust "floating" on a dense underlying layer; areas of less dense continental crust rise topographically above more dense oceanic crust

Little Ice Age

interval of nearly four centuries (1300 A.D. to the mid- to late 1800s) during which glaciers expanded to their greatest historic extents

Milankovitch theory

explains cyclic variations in climate as a consequence of irregularities in the Earth's rotation and orbit

Pleistocene Epoch

first of two epochs comprosing the Quaternary Period. commonly called the Ice Age. occrred between 1.6 million and 10,000 years ago

pluvial lake

any lake that formed beyond the areas directly affected by glaciation during the Pleistocene as a result of increased precipitation and lower evaporation rates, e.g., Lake Bonneville

pollen analysis

identification and statistical analysis of pollen from sedimentary rocks; such analyses provide information about ancient floras and climates

proglacial lake

lake formed by melt-water accumulating along the margins of a glacier

Quaternary Period

term for a geologic period or system comprising all geologic time or rocks fro the end of the Tertiary to the present; consists of two epochs or series, the Pleistocene and the Recent (Holocene)

most recent ice age occurred during

Pleistocene Epoch

how many years ago did the Pleistocene Epoch begin

1.6 million

in addition to glaciation, the Pleistocene is known for

volcanism, folding, faulting, and uplift

during the Pleistocene most of the world was what compared to today

drier

pollen analysis can reveal past

vegetation, climate

cool period from about 1500 to the mid- to late- 1800s is known as

Little Ice Age

unsorted sediment directly deposited by a glacier is

till

North American glacial stages

Wisconsin, Illinoian, Kansan, and Nebraskan; named for the states representing the farthest advace where deposits are well exposed

the three interglacial stages

Sanamon, Yarmouth, and Aftonian; named for localities of well-exposed interglacial soil and other deposits

can be used to detremine oceanic surface temperatures during the Pleistocene

O18 to O16 isotope ratios; identification of planktonic foraminiferal species; coiling ratios of planktonic foraminiferal species; and ocean chemistry

lakes that formed far from glaciers during times of glaciation in what are now dry areas are known as

pluvial

phenomenon in which the crust sinks and then rises as a result of loading by glaciers followed by melting

isostasy

formation of land bridges such as the one across the Bering Straits or between Europe and England during the Pleistocene resulted from

a drop in sea level

parameters Milankovitch used to explain the glacial-interglacial episodes of the Pleistocene

the degree to which the orbit departs from a perfect circle; the angle a line perpendicular to the plane of the ecliptic; the precession of the equinoxes

short-term climatic events can be explained by

variation in solar evergy and volcanic reputions

important Quaternary mineral resources

gold placers, sand, gravel, and borax

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