Vegetation and Topographic Signature of Life Flashcards
What are the controls of rainfall and subsequently also of vegetation?
Atmospheric Circulation: Tri-cellular model
Continental Isolation; The more inland the less rainfall
Rain Shadow: Places within it experience little rainfall
Ocean Circulation: Areas that receive colder water will experience less cloud formation
What is the rain shadow effect?
A raincloud travelling over a high altitude region will condense on the side it travels over first because of the orographic rainfall. So when they travel over the other side there is little moisture left to condense
Give an example of where the ocean circulation has altered rainfall patterns over a small area
In South Africa’s western coast the Benguela brings colder water from Antarctic, whereas on the Eastern coast the Aghulas brings warmer water from equator.
What does a lack of vegetation in an area expose it to more?
Aeolian process
What are Aeolian transportation processes?
Suspension (Finest particles carried by turbulent eddies over long distances)
Saltation (coarser particles bounce along the surface transferring the momentum to ground impact)
Creep (Larger particles are slowly pushed and slid along the surface)
What is the most dominant Aeolian transportation method?
Saltation
What differentiates Aeolian transportation methods form fluvial?
Fluvial can transport larger particles
What are desert pavements?
Areas where Aeolian processes have removed finer sediment leaving a gravelly pavement of coarser sediment
What are ventifacts?
Large structures shaped by abrasion (Sand blasting). shape determined by wind direction and object orientation
What are Yardangs?
Larger than ventifacts these are ridges separated by chutes determined by the abrasion of windblown sand
What are inselbergs?
Isolated mountains of resistant rock that have been exposed by erosion around them
What are sand seas/ergs?
Huge dumps of Aeolian sediment downwind covering a large geographical area
What are the most commonly occurring landforms within sand seas/ergs?
Dunes
What are the four types of dune?
Barchans
Transverse
Longitudinal
Parabolic
Describe Barchans dunes
Isolated, face downwind, form when sediment supply is limited and strong winds
Describe Transverse Dunes
Perpendicular to wind direction, form when sediment supply is large, strong steady winds. They are typically a merging of barchans to form long wavy ridges
Describe Parabolic Dunes
Facing upwind, common in coastal areas, form when sediment supply is moderate to large and wind direction is constant, Assisted by the presence of vegetation
Describe longitudinal dunes
Parallel to wind direction, form when low to moderate sediment supply, minor variation in the wind direction
How does vegetation affect the structure of soils?
- Absorbs moisture to usually where it occurs the upper layer are drier
- Vegetation secures soil by reducing pore space on slopes mitigating mass movement probability
How does agriculture impact vegetation and the hydrological cycle?
It removes vegetation which increases runoff and weaken the soils leading to increased erosion.
Grazing can also cause compaction which increases runoff
Both of these reduces soil quality and thickness
How does deforestation affect vegetation and therefore the external river aspects?
It cause instability and erosion causing soil thinning. This increases river sediment load which affects systems at the river mouth
How does vegetation influence the internal aspects of rivers?
Vegetation near the banks can increase bank strength. Vegetation may also colonise the middle of the channel leading to island formation. Roughness. Sediment transport and floodplain development.
What are ephemeral channels?
These are wide channels occurring in upland areas because the vegetation is sparse due to conditons. The flash-flow rainfall combined with this increases flooding.
What are Arroyos channels?
Deep channels created through river incision provoked by climate and land use change
What was the conclusion of Tal & Paola’s study?
Without vegetation channel was split in to multiple shallow flows. With, there was one narrow deep flow due to colonisation of bars preventing lateral processes.
What is the topographic signature of life?
The idea that the presence of life has a significant stamp on the landscape.
Is there a topographic signature of life?
From studying mars, there doesn’t appear to be as there are many landforms that exist there despite the planet not having any indications of previous or current life. Vegetation only appears to tweak the environment.
