AGEN2363 Chpt. 3 notes. Geologic erosion and sedimentation.
I. Geologic erosion/sedimentation – ‘natural’ processes: 1) slow, 2) catastrophic.
Three factors related to geologic erosion/deposition:
1. Source of the material. Soil parent material.
loess – wind-blown silt loam soils, most erosive.
recent volcanic ash deposits – clay to fine sandy loam, very erosive.
residium – weather rock, more resistant.
alluvial – flood plain deposits, variable erosiveness
marine – sediments from old marine bays, estuaries, marsh plains
colluvial – gravity erosion deposits at hill bases
glacial till – sediments from continental glaciers
eolian – wind-blown dunes, silty to fine sandy loam, very erosive to wind
lacustrine – old lake beds.
2. transporting agent: water:
- rainfall, - intense storms from hurricanes, fronts, and localized convection
- runoff, - intense runoff from melting snow, floods, breaks in natural dams, etc.
- ‘creep’ (define)
- ‘saltation’ (define)
- tectonic liquification (define)
- rivers, streams, flood plains, and intermittent streams
wind: ‘normal’ and catastrophic from storms, major climate changes from glaciers
3. environment: relates to the topography, climate, and vegetation.
Older landscapes and landscapes along major rivers, lakes, and oceans tend to be
more dissected and hilly.
Uplift, due to upward/downward continental mass movement increases elevation,
slope, erosion and ‘warps’ rock sediments.
Geomorphology – study of earth’s surface forms and processes that shape them. Relates to the landscape that forms and effects on erosion and deposition. The past climates serve dramatically influenced the landscapes we see today.
II. Geographical cycle: three processes:
1. Structure. physical nature and arrangement of the rocks and sediments.
2. Process. Refers to energy of mechanisms that influence geomorphology
such as water, wind, and mass movement (‘creep’, glaciers, mudslides, etc).
3. Climate. Past and present. Effects on wind, water, and vegetation.
Interpreting the effects of landscape age on the geomorphology depends on the age and
source of the soil and rock, and the three processes above.
In Arkansas, these events have shaped the landscapes we see today the most:
- continental glaciers, - uplifting, - catastrophic floods, - EARTHQUAKES!
- and believe it or not, VOLCANOES! (‘crater’ of diamonds state park)
Buried landscapes can be found in areas of deposition, dune landscapes, colluvial and alluvial plains, volcanoes, and areas prone to mudslides and flooding.
III. Other terms and processes you need to know:
- ‘dendritic’ stream pattern
- stream ‘terrace’: primary, secondary, tertiary
- stream ‘levee’
- alluvial ‘fans’
- peat bogs
- evaporative deposits
- continental glaciers
- geologic erosion
(Please note: review the questions at the end of each chapter to determine if you have grasped the material or not. If you are comfortable with your ability to answer the questions at the end of the chapters, you will most likely do well on the exams.)