Lecture 12: Landform development Flashcards
Describe how alluvial fans form
When fast-moving streams emerge from a mountainous region onto a flatter plain, they lose energy and deposit sediment in a fan-shaped formation. These alluvial fans typically consist of coarser material near the apex and finer sediments further away.
Describe how Stream Floodplains and Terraces form
When a river overflows its banks, it spreads sediment across the adjacent low-lying area, forming a floodplain. Over time, as the river cuts deeper, older floodplains are left at higher elevations, forming terraces. These terraces mark former levels of the riverbed.
Describe how a delta is formed
At a river’s mouth, where the flow velocity decreases as it meets a standing body of water, sediment accumulates, forming a delta. Deltas are characterized by a branching, distributary network that deposits fine sediments like silt and clay.
How can short term denudation rates be measured?
Modern denudation rates can be calculated by measuring the
amount of sediment reaching the
ocean
How can long term denudation rates be measured?
Long-term denudation rates can
be calculated by measuring
sediment in transport, temporarily
stored on landscape, and sediment stored in ocean basins
What processes drive uplift?
- Tectonics, isostasy, and volcanism drive uplift
What processes drive denudation?
- Gravity and solar energy drive denudation
Weathering etc.
Can a landscape reach equilibrium?
A landscape never achieves a state of equilibrium, it is, and likely always has been, a dynamic surface
What is a peneplain?
Peneplain = final stage landform
development typically taking long interval of geologic time
What are the Factors Controlling Landscape Development?
Landform development
in any given location is
controlled by
* Process
* Climate
* Lithology
* Relief
* Time
Rough country has ‘high relief’,
Flat country has ‘low relief’
What is the difference between consequent streams and subsequent streams?
Consequent Streams – Pattern is a
consequence of the regional slope of the land and reflects gradual uplift.
Subsequent Streams – have adjusted to
follow zones of easily eroded rock.
What is stream capture?
Stream capture – Headward erosion causes one stream to be diverted to the basin of another stream naturally
What is the difference between antecedent streams and Superposed Streams?
Antecedent Streams – have maintained an earlier course in a region being uplift by folding or faulting. The streams
characteristically flow across strike of strata and faults ignoring topography.
Superposed Streams – “letdown” by an earlier course developed in softer, uncomformably overlying cover strata. The stream bed was lowered into a concealed resistant basement and continued flowing in its original course.
