Glacial Landforms 2 Flashcards
(21 cards)
What is a medial moraine?
A ridge of moraine down the middle of the valley floor.
Medial moraines form when two valley glaciers converge and their lateral moraines combine.
What is a lateral moraine?
A ridge of moraine along the edge of the valley floor.
Lateral moraines are formed by the weathering of exposed rock on the valley side.
What is a recessional moraine?
A ridge of moraine extending across the valley at the furthest point the glacier reached.
Recessional moraines indicate periods of still-stand during ice retreat.
What is a terminal moraine?
A ridge of moraine at the furthest point of glacier advance.
The up-valley side of a terminal moraine is generally steeper due to the advancing ice.
What are drumlins?
Smooth, elongated mounds of till, with a long axis parallel to the direction of ice movement.
Drumlins have a steep stoss and gentle lee slope topography.
What are erratics?
Pieces of rock that differ from the surrounding rock and are transported by glacial ice.
Erratics are often found far from their source due to glacial movement.
What is the formation process of a medial moraine?
When two valley glaciers converge, two lateral moraines combine to form a medial moraine.
Material is carried and deposited when melting occurs, and the moraine is parallel to ice flow.
How are lateral moraines formed?
Exposed rock on the valley side is weathered, and fragments fall onto the edge of the glacier.
These fragments are carried along the valley and deposited when the ice melts.
What does a recessional moraine indicate?
Periods of still-stand during ice retreat.
They are good indicators of the cycle of advance and retreat that glaciers experience.
Fill in the blank: A _______ moraine represents a ridge of moraine that forms at the furthest point of glacier advance.
terminal
True or False: Drumlins are formed by deposition when glacier ice becomes overloaded with debris.
True
Drumlins are shaped by indicators of the direction and velocity of past ice movement.
What is a till plain?
A large, relatively flat plain or undulating landscape of till in a lowland area (also called ground moraine).
What characterizes lodgement till?
Deposits of angular rock fragments (clasts) in a fine matrix (rock flour) - unstratified, unsorted, and containing erratics.
What is ablation till?
Till deposited by melting ice from stationary or retreating glaciers, forming landforms such as terminal and recessional moraines.
How is till formed?
When a sheet of ice retreats, large amounts of material are deposited over a sizeable area due to melting.
True or False: Till is sorted and layered.
False
Fill in the blank: Till is deposited by melting ice from _______ or retreating glaciers.
stationary
What are erratics?
Large rock fragments that differ from the surrounding geology, found within till deposits.
What type of landscape does a till plain represent?
A lowland area.
What is the matrix in lodgement till composed of?
Rock flour.
What are terminal and recessional moraines?
Landforms formed by till deposited from melting ice.
