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43 terms

Geology Ch 18

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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