1.5 million yrs
Basaltic lava flows
Boundary between parts of the glacier moving by basal sliding and crevassal slip
Boundary between the basal sliding and external flowage zones
Bottom of the basal sliding zone
Top of the internal deformation and flowage zone
Wastage exceeds accumulation.
Accumulation exceeds wastage.
Accumulation and wastage are about equal.
None of the above
The internal, flowage zone
The snout zone
The surface, brittle zone
The basal, sliding zone
Cirque and terminal moraine
Outwash plain and horn
Hanging valley and truncated spur
Drumlin and fiord
Terminal, valley or alpine glacier
Terminal, continental ice sheet
Recessional, continental ice sheet
Lateral, valley or alpine glacier
Cores from sea ice in the Arctic Ocean; NaCl content
Sediment cores from a terminal moraine in Ohio; sand-to-clay ratio
Sediment cores from a Pleistocene loess deposit in the state of Mississippi; SiO2 content
Cores from the Greenland ice sheet; ratios of the oxygen isotopes (0-18/0-16)
The climate cools suddenly and a retreating glacier begins to advance
Heavy snowfalls resulting in avalanches in the zone of accumulation
Melting at the base of the glacier resulting in increased rates of basal slip
Crevasses opening suddenly near the snout of a glacier
Deposited directly from melting ice
Sand and gravel beds
Deposits are often layered and well-sorted
Deposited by glacial meltwater streams
Terminal moraines of continental ice sheets that moved south from Canada
Old shorelines of large, pluvial lakes
Erosional features produced by continental glaciation
Subaerial deltas submerged by the post-glacial rise in sea level
A stream valley, deepened by glacial erosion, that floods as sea level rises
A glacier-cut valley that is dammed by an end moraine and a large lake is formed
A glacier-cut valley which sinks below sea level due to glacial rebound after the ice melts
A large, kettle-pocked moraine left as an island when sea level rises following melting of the ice
Indianan, Kansan, Nebraskan, Ohioan
Kansan, Illinoian, Iowan, Dakotan
Nebraskan, Indianan, Illinoian, Wisconsinan
Nebraskan, Kansan, Illinoian, Wisconsinan
Ice sheets are larger than ice caps.
Piedmont glaciers form on lowlands at the base of mountainous terrain.
The volume of water tied up in the Antarctic ice sheet is about the same as the total discharge of the Amazon River in one year.
Long, extended, alpine glaciers occupied valleys in most high, mountainous areas in the United States, Canada, and Europe at one or more times during the past two million years.
Smooth, tapering ridge of till; formed and shaped beneath a continental ice sheet
Bowl-shaped depression eroded largely by frost action and glacial plucking
Till mound of outwash deposited by meltwater streams at the snout of a glacier
Smooth, striated, bedrock ridge shaped and polished by a glacier
Terminal moraines and cirques
Outwash plains and valley trains
Valley moraines and ice sheet trains
Recessional kettles and erratics
By calving of large piedmont glaciers in Greenland
As large masses of sea ice that float northward from Antarctica
As masses of sea ice that float southward from the Arctic Ocean
As calved blocks of glacial ice that float northward from Antarctica
Floating of icebergs southward from the north polar seas
Slow, plastic flow movement in the brittle zone of a glacier
The sedimentary materials outwash and till
The slow, southward advance of the continental ice sheets over Canada and North America during the Pleistocene
Till is deposited directly from the ice; outwash is deposited by meltwater streams.
Glacial erratics are blocks of rock that are too large for the glacier to move.
Tills are poorly sorted and the fragments are mostly angular.
Outwash is mainly stratified sand and gravel.
Movements of Earth's tectonic plates
Variations in the Sun's energy output
Precession of Earth's orbit
Wobbling of Earth's rotational axis