Asylum Walk (18)

Geological terms. From a notebook left in Room 6:

“The river supplies an adequate cause for executing the task assigned to it.” (Charles Lyell, diary 1841, disputing catastrophic causes of the Niagara gorge)

Unconformity: A surface of erosion or non-deposition that separates younger strata from older rocks. It represents a long interval of time.
Drift: Material deposited by glaciers.
Moraine: An accumulation of drift deposited by glacial action and possessing initial constructional form independent of the floor beneath it.
Erratics: Rocks different from the bedrock they are found in, transported and deposited by glaciers.
Isostatic rebound: The tendency of land depressed by the weight of glaciers to spring back after the glaciers have retreated.
Mass wasting: The downslope movement, often in the form of spectacular falls, of soil and rock under the direct influence of gravity.
Talus: Fallen rocks, the result of mass wasting, at the foot of a steep slope such as the face of an escarpment.
Varve: A pair of seasonally deposited sediment layers, one layer in summer, the other in winter. Thus one varve represents one year.