Notes on the Quaternary Period and Pleistocene Glaciation

Quaternary Period Overview

  • Last 2.6 million years of Earth history, includes Pleistocene and Holocene Epochs.

  • Significant changes: widespread glaciers, emergence of anatomically-modern humans (genus Homo).

Pleistocene Paleogeography

  • Maximum Pleistocene glaciers covered Northern Hemisphere and Antarctica.

  • Boundary between Pleistocene and Holocene set at 11.7 ka; marked by climate warming and ice sheet retreat.

  • Evidence from vegetation changes and oxygen isotope ratios in marine organisms.

Ice Sheet Formation and Characteristics

  • Glaciers: moving bodies of ice formed when snow accumulation exceeds melting (glacial budget).

  • Mountain glaciers (topography constrained) vs. ice caps (unconstrained) vs. continental glaciers (largest ice sheets).

  • Maximum Pleistocene glaciation covered 30% of Earth's land.

Antarctic Ice Cap and Laurentide Ice Sheet

  • Antarctic ice sheets began forming ~40 Ma, current area ~14 million km², average thickness >2 km.

  • Laurentide ice sheet originated from Greenland, reached maximum extent of 13 million km² and thickness up to 4 km at the Last Glacial Maximum (18 ka).

Glacial Dynamics

  • Glacier zones: accumulation zone (where snow is added) and ablation zone (where melting occurs).

  • Equilibrium line denotes meeting altitude of both zones; changes affect glacier size and stability.

Effects of Glaciation

  • Types of landscapes from glaciation include ice-scoured plains, U-shaped valleys, and distinctive geological features like moraines.

  • Specific examples include the Cape Cod end moraine and midcontinental moraines from Wisconsinan glaciation.

Climate Changes and Sea Levels

  • During Pleistocene, sea levels were 130 m lower; Bering land bridge exposed, facilitating migrations.

  • Glacial melting could potentially raise sea levels by 70 m today.

Isostasy

  • Isostatic rebound relates to the vertical movement of the Earth's crust due to glacial mass changes.

  • Areas previously covered by glaciers show ongoing rebounding since Pleistocene.