A:Hot and Semi-Arid Environments Flashcards
(20 cards)
Define Aridity
An area that is extremely dry, with low levels of precipitation and high rates of evapotranspiration- therefore is unable to support most plants
What is the aridity index
Relationship between actual evapotranspiration compared to potential evapotranspiration
Define actual evapotranspiration
Sum of evaporation and plant transpiration from Earth’s surface to atmosphere
Define potential evapotranspiration
Amount of evaporation that would occur if enough moisture was freely available to vegetation all year round
Where do the majority of the worlds arid areas lie
Between 15-30 degrees North and South of the equator. Also generally found on the west coast of continents
What is rainfall effectiveness
Actual Precipitation- Evapotranspiration
Apart from the aridity index, what are other ways of defining aridity
Annual Rainfall
Average Annual Temperature
Rainfall Effectiveness
Characteristics of Hyper-Arid
- Rainfall infrequent with less than 100mm a year
- Vegetation absent apart from a few scattered shrubs
- For example Northern Edge of the Sahara Desert
Characteristics of Arid
Rainfall unreliable, less than 250mm a year
-Sparse vegetation consisting of grasses and shrubs
Characteristics of Semi-Arid
- Rainfall seasonal and more reliable, less than 500mm a year
- Variety of grasses, shrubs and trees
- High Atlas Mountains of Morocco
Define a Dryland
Drylands are characterised by a scarcity of water, which affects both natural and managed ecosystems and constrains the production of livestock as well as crops
Define Desertification
The process of land degradation in arid and semi-arid regions, resulting from various factors both climatic and human
Causes of Desertification x9
- Deforestation
- Population Growth
- Climate Change
- Urbanisation
- Over-grazing
- Tillage practises
- War
- Natural Disasters
- Lack of precipitation
What is a pluvial
A period of increased moisture availability
What period of geology are we currently in
Quaternary
when was the tertiary period
The period between 2.6 million-65 million years ago
Potential reasons for the changes in geological period
- Changes in patterns of the earths orbit
- Uplift of mountain ranges
- Changes in the position and configuration of the land masses due to continental drift
- Changes in water circulation deep in oceans
- Development of ice sheets due to glaciation
What is an inter pluvial
A comparatively dry period between pluvials
What is an inter-glacial
A period of milder climate between 2 glacial periods
Evidence for changes in the extent of aridity
-Cave paintings show animals such as Elephants that now live in wetter Savannah further south
-Sediment Cores-
Shrunken Lakes
-Calcrete
-Fossils
-Dendritic Patterns
