SUSTAINABLE MANAGEMENT – RAINFORESTS

Due to the sheer speed and scale of deforestation in the world’s rainforests, sustainable management techniques have been put into place to reduce the impact. I will discuss these shortly.

It does make you wonder to what extent rainforests can regenerate naturally without human intervention. If small areas of rainforest are cleared at a small scale then left alone, the rainforest can regenerate. However, the large-scale deforestation breaks the natural nutrient cycle. This in turn affects the soils and leaves the soil subject to erosion where the land has been cleared. Then when the rains come, more nutrients are lost as they are washed away. In turn, the land becomes infertile with new tree roots being unable to establish themselves. The ecosystem dies and the land remains empty. The loss of trees in the area results in the global oxygen and carbon dioxide balance changing which is believed to contribute to global warming.

Sustainable management

Exploitation of the rainforests is causing severe global consequences. If this continues in an uncontrolled way, irreversible damage could be done to the rainforests. This is why sustainable forest management is needed.

Sustainable management can be seen in the Amazon rainforest. There are currently three main aims that have been put into place:

·         To protect the rainforest canopy and bio-diversity, preventing soil erosion

·         To maintain the operation of the nutrient cycle

·         To ensure the natural regeneration of the forest

These aims are accompanied by a range of strategies:

·         Agro-forestry – Growing trees in line with agricultural crops. Allows farmers to use the trees as a protective canopy for their crops and also have a supply of nutrients from decomposing plant matter.

·         Forest Reserves – Ensure areas of forests are completely protected from any type of human activity allowing growth of sustainable products such as plants for medicines and latex from rubber tapping.

·         Tree measuring – Trees should only be felled once they have reached a certain height which ensures younger trees have a chance of survival.

·         Afforestation – Planting new trees when mature trees have been felled in attempt to maintain the canopy.

·         Education – Ensuring those who use the rainforest know how to in a sustainable manner.

·         Selective logging – Ensuring trees are only felled once they have matured. This helps preserve the existing canopy, and helps the slower growing hardwoods such as mahogany (see previous post about hardwoods).

Students can use this link as a potential case study which shows a comparison of the Pacific ACP states rainforest’s: http://ec.europa.eu/development/body/publications/courier/courier193/en/en_030.pdf.

The S-cool revision website is a useful source when studying this area which covers other areas such as tourism and ecotourism in the tropical rainforests as well. See: http://www.s-cool.co.uk/a-level/geography/ecosystems/revise-it/managing-the-tropical-rainforest.

This is an article showing that despite sustainable management strategies being put into place, it is only occurring in small areas of rainforest and there is still much development needed. Despite the attempts to add protection to the forests making them areas of non-activity, it has been noted that only 3% of rainforests worldwide between 2005 and 2010 were protected. See the following article for more details: http://www.nature.com/news/2011/110608/full/news.2011.308.html.

This final link shows a video of rainforests in Indonesia and Costa Rica and the impact of destruction and sustainable management on them. Students will find this very beneficial to watch: http://www.bbc.co.uk/learningzone/clips/rainforest-destruction-kalimantan-indonesia-and-costa-rica/3096.html

 

Links:

http://www.aqua.org/explore/baltimore/exhibits-experiences/upland-tropical-rainforest

http://lornali.com/sustainable-rainforest-management

http://www.amazoncharitabletrust.org/en/index.asp

http://www.bbc.co.uk/schools/gcsebitesize/geography/ecosystems/human_uses_rainforest_rev5.shtml

HUMAN IMPACT ON THE RAINFOREST

Hundreds of years ago rainforests were not under threat human activities. Despite rainforests catering for small tribes of people, these tribes had very little effects on the ecosystem. However, today rainforests are under great threats as ‘our’ actions are destroying them – rapidly! The main problem is deforestation!

Deforestation is happening quickly! Too quickly! Trees are being felled at a much quicker rate than what they are growing at. It is feared that by 2030 the world’s rainforests may be gone. To put this into perspective, in the Amazon it is thought that 2.5 hectares of forest are cleared each minute! This is the equivalent of 5 football pitches! (I will make reference to the Amazon throughout this post to give an outline of the scale of the human activities listed below).



Logging



Economic exploitation

Logging – there is a high demand for hardwoods such as mahogany and rosewood from the rainforests. Consumers in MEDCs will pay a lot of money for furniture made by these woods. However for every tree cut down it is believed that 30 others may be damaged or destroyed in the process. Five million hectares of forest are lost in the Amazon as a result.  

Mining



Mining – Some rainforests have developed above mineral rich resources. One of the main minerals found in Amazon rainforest is iron ore, also known as haematite. This is mined and exported to steel making countries. However this mining process is destroying huge areas of forest in the process. Iron ore is not the only mineral found in the rainforest, other metal ores such as gold, platinum, copper, lead, and bauxite can be found.



Cattle ranching



Cattle ranching – Another reason for the clearing of land is so farmers can rear their cattle. Since 1950, it is estimated that two-thirds of the Amazon’s lowland forest has been turned into pasture for grazing. Due to overgrazing, the nutrients in the soil decline making the quality of the grass poorer. This has resulted in ranches expanding their land for better quality soil and grasses.



Peasant farming – This is at a much smaller scale, but due to over-crowding in cities (particularly in Brazil) citizens have been pushed into the rainforest with permission to clear land for farming, however due to infertile soils, this has not been entirely successful.

 

I have found a useful link that provides a work sheet used in a school for Year 10. I think it would be effective for students working at GCSE level to take a look at it. It can be found on: http://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&frm=1&source=web&cd=10&sqi=2&ved=0CHIQFjAJ&url=http%3A%2F%2Fwww.geography.learnontheinternet.co.uk%2Fvgd%2Fresources%2Fyear10%2Fecosystems%2Fwhatistheimpactofhumansinthetropicalrainforest.doc&ei=b7I3ULWJEuLS0QWZyYGQDg&usg=AFQjCNGrViY4d25e6KOBISE41rFxgNqoXA&sig2=IKoRFTq7ku4yfic84BEM7Q

 The National Geographic has provided lesson ideas and activities that can be used within the classroom with high school students. Some of the activities are very time consuming however may provide inspiration when developing personal lesson activities. See: http://www.nationalgeographic.com/xpeditions/lessons/14/g912/fayhuman.html

 

Links:

http://www.rain-tree.com/facts.htm

http://biology.clc.uc.edu/courses/bio303/human%20interactions.htm

RAINFOREST STRUCTURE

Rainforests have four distinct layers. These layers have formed based on the light available to plants which they need for photosynthesis.

These layers are:

·         The emergent layer - these trees (emergents) have broken through the canopy layer, growing taller than most trees in the battle for light. These trees can reach 50-60m in height and have trunk circumferences that can measure up to 5m. These trunks are usually supported by buttress roots, which also help protect the trees from strong winds. These trees are exposed to greater climatic and weather conditions than the other layers due to their exposure and therefore their leaves tend to be thick and waxy and hold water. Being above the other layers allows the trees to make good use of the wind to disperse seeds and fruits. This layer supports wildlife such as eagles, monkeys, butterflies, bats and snakes.

·         The canopy - also known as the primary layer. Emergents grow up to 45m. This layer can block 80% of the light reaching the under-layers of the rainforest creating high competition among many plant species. However the canopy also acts as a shield, blocking heaving rain from destroying the plants below. Thick, woody vines can be found in this layer, known as lianas, which grow up trees in the search for sunlight. In the canopy animals such as monkeys, sloths, bats, treefrogs, ants, beetles, parrots and other bird species can be found here.

·         The under canopy – also can be referred to as the ‘under-story’. This layer only receives around 2-5% of the sunlight available to the canopy. The plants that grow in this layer have adapted to make use of the little light they receive by having dark green leaves that take in more light than lighter leaves, in other words they are ‘solar collecting’ leaves. These plants also refrain from growing flowers to conserve more energy. Plant pollination is much harder on this layer due to the lack of air movement. Animals such as snakes, parakeets, leopards, jaguars and a range of insects can be found here.

Rainforest structure

·        The shrub layer – this is the forest floor and very few plants grow on this layer due to it only receiving between 0-2% of the sunlight and has 100% humidity. This layer hosts rapid decomposition of vegetation and other organisms that are broken down into nutrients that are recycled back into the rainforest. Insects, cockroaches, beetles, centipedes, millipedes and earthworms can be found here among mosses, herbs and fungi.



The BBC Learning zone website provides a video and teaching tips
when covering the rinforest structure in the classroom. See:
ttp://www.bbc.co.uk/learningzone/clips/rainforest-structure-layering/3092.html

Links:

http://library.thinkquest.org/27257/structure.html http://www.srl.caltech.edu/personnel/krubal/rainforest/Edit560s6/www/whlayers.html
http://www.geography.learnontheinternet.co.uk/topics/rainforest.html

TROPICAL RAINFORESTS

I remember studying in depth tropical rainforests for my GCSE’s. It was definitely an area that captured my interest more than others. However, just like everything I have studied feel I would not be able to talk about these in great depth without some revising first.

I am particularly excited to write a few posts on this area as I had the privilege of visiting the Amazon rainforest earlier this year and feel I can strongly relate to it.



Rainforest locations



Tropical rainforests are located in the tropics where the climate is hot and wet all year. They currently cover 6% of the Earth’s which has significantly decreased over the past 200 years where they used to cover twice as much.



Tropical rainforests are considered the most ecologically bio-diverse ecosystems on the planet:

-          They are home to 50% of all life-forms on the planet

-          They produce 40% of the worlds oxygen

-          The vegetation is dense with trees growing up to 50m in height.

The climate

Tropical rainforests do not tend to have distinct seasons, if any seasons at all. The day to day climate is usually the same all year round. The weather tends to be either hot and dry or hot and wet with occasional thunder storms. The average daily temperature is around 28°C which can reach 35°C and will never fall below 20°C and on average will receive around 2000mm of rain per year, creating a ‘sticky atmosphere’. I can agree that the rainforest was all of these... hot, muggy, humid, damp... Not the easiest conditions to live in to say the least!



Soil and nutrient cycle



The rainforest can be quite deceptive with its dense vegetation and range of exotic wildlife. It may be a lush paradise but in reality they have fragile ecosystems with poor soils. There tends to only be a thin layer of fertile soil on the grounds surface with the deeper soils being ‘iron-rich laterites’ which are not good for vegetation growth. The majority (80%) of the nutrients available in the forest actually come from the vegetation itself, when plant matter falls to the ground and decomposes rather quickly due to the hot wet climate. This allows the nutrients to be recycled back into the forest (see diagram).

Students may find the diagram useful to sketch to help remember the cycle.  



Links:

http://www.rain-tree.com/facts.htm

http://www.aqua.org/explore/baltimore/exhibits-experiences/upland-tropical-rainforest

http://www.bbc.co.uk/schools/gcsebitesize/geography/ecosystems/tropical_rainforests_video.shtml  

HUMAN IMPACT ON THE SAVANNA

Humans can have negative impacts on the savanna if their activities are not controlled. These can lead to areas of the savanna becoming deserted.

These activities include:

·         Man-made fires – These are made to burn areas of grassland to help aid the better growth of young grass in subsequent seasons. The use of fire however, destroys particular plant species who cannot withstand the fire, leaving areas to only accommodate pyrophytic plants species such as the baobab and acacia tree. Also fires can damage the soils making it harder for vegetation to grow in certain areas.

·         Grazing – Cattle grazing results in certain plants being killed leaving behind the so-called animal repellent plants behind such as thorny bushes, shrubbery and acacia trees. Also areas are cleared for farmland which in some extremes can lead to desertification of the area when the soil becomes infertile.

·         Hunting – Some animals in the savanna are hunted for their valuable body parts e.g. elephants for their tusks, lions for their fur and bison for their meat. Many animals have been hunted to the point they are verging on extinction. Despite certain measure being put into place, only 1% of grasslands are protected by the Government.

Here’s another video from BBC Bitesize to help students: http://www.bbc.co.uk/schools/gcsebitesize/geography/ecosystems/savannah_grassland_video.shtml. I am not keen on the video as I do not think it gets the point across effectively due to it being so brief, however I am currently struggling to find a more useful video.

And so it has taken me 15 posts to establish how to get a video onto the blog, it feels quite an achievement to say the least as I am no computer expert. This second video shows an African savanna, it shows what a savanna looks like, how it accommodates particular animal species and how the species are playing a role in shaping the savanna.  

Links:

http://www.ecologyandsociety.org/vol7/iss1/art9/des_human_influence.html

http://www.sln.org.uk/geography/schools/blythebridge/gcseecosystemsavanna.htm

VEGETATION IN THE SAVANNA



Elephant grass



The savanna hosts a range of vegetation, these plants however have adapted to survive in this varying wet and dry humid climate.

In the wetter areas, tall coarse grasses known as elephant grass can be found among many deciduous trees (these trees lose their leaves in the dry season). This is known as the tree savanna. In the drier areas, shorter tufts of grass grow known as tussock grass. This grass is usually accompanied by two types of drought resistant trees, the baobab and the acacia.

Tussock grass

The baobab tree – Also known as the ‘upside-down tree’ has a thick spongy trunk, long tap roots and bears leaves for only a few weeks.

The acacia tree – These have a crown structure, often flattened by the trade winds. These trees lose their leaves in the dry season.

These trees are pyrophytic meaning they can withstand fire mainly due to their insulating bark. They also have leathery leaves to reduce transpiration losses. Other plants are microphyllous, meaning they are small leaved to also reduce transpiration losses. 



Acacia tree



In the tree savanna a so-called ‘parkland’ exists. The trees crown shaped tops shade the root areas and help prevent soil moisture evaporation. These trees show xerophytic characteristics meaning they have adapted to survive in dry environments that lack water. These characteristics include:



-          Dense cell fluids

-          Hard waxy leaves

-          Thorns

-          A protected stomata

Baobab tree

These all help reduce water loss. 

Outside the tree savanna is the grassland savanna where the grasses between the trees become shorter and sparser. The grass tends to die back in the dry season and regrow from root nodules when it rains. Beyond the grassland savanna, is the shrub (scrub) savanna. Here you can find short tufted grasses, acacia trees and thorn bushes. In the shrub savanna, vegetation compete for water and have the ability to turn their blades away from the sun to reduce water loss.

For a better understanding students can watch the savanna grassland video on BBC Bitesize: http://www.bbc.co.uk/schools/gcsebitesize/geography/ecosystems/savannah_grassland_video.shtml



Links:

http://www.blueplanetbiomes.org/savanna_plant_page.htm

http://www.pupilvision.com/uppersixth/savanna2.htm

https://php.radford.edu/~swoodwar/biomes/?page_id=105

THE SAVANNA

Now I have studied the savanna at GCSE level and believe it to be another extreme landscape. Yet again, this is another area I do not remember in much detail due to studying it so long ago.

So, what is a savanna?

Now a savanna is not a desert. A savanna is a large area/space of grassland that comprises of widely spaced trees. Savannas can occur in several types of biomes and consist of a range of flora and fauna. They are enormous plains that are found between moisture equator forests and tropical deserts, and consist of various layers.

Savannas have a wet season (summer) and a dry season (winter) so only certain vegetation can grow there, however the conditions are suitable for a range of animal types. In the wet season savannas can receive on average between 15 and 25 inches of rainfall, however only around 4 inches of rainfall is received in the dry season.



African savanna



Savannas can be found in areas of Africa, in South America (mainly Brazil) and Northern Australia with the largest being found in Africa. It is Africa’s savannas that boast the most wildlife species and it is these savannas we often refer to. In Eastern African savannas such as the Serengeti Plains of Tanzania, lions, zebras, elephants, giraffe and many types of ungulates (which I have learnt today means  animals with hooves) inhabit the area. These animals migrate in the dry season to areas where more rainfall occurs due to the lack of vegetation available to graze on in the dryer areas.




Savanna transect

 

The type and density of the vegetation changes with latitude. Closer to the equator is the ‘closed’ savanna, with just a short drought season and therefore there is a greater amount of trees. Closer to desert areas, it is known as the ‘open’ savanna. This has a much longer drought season, little can grow here so shrubs and clumps of grass dominate these areas. Students may find the transect (see diagram)useful to understand how the types vegetation can vary across a savanna.

I think it is important for students to know this diagram and how the land and vegetation changes as you move away from the equator. It is particularly important as I have already covered the desert, I am currently covering the savanna and I will be posting about tropical rainforests shortly. Therefore this diagram is useful to use and refer back to.

Links:

http://www.worldstory.net/en/savana/the_savana.html

http://www.blueplanetbiomes.org/savanna.htm

http://www.geography.learnontheinternet.co.uk/topics/savanna.html

FROM OFF TOPIC - TO A CASE STUDY

Ok, I’ve lost myself a little with my off-topic investigations but now back to desertification.

The Sahel

An example of desertification is in the Sahel, a vast strip of land to the south of the Sahara Desert.

This is an extreme area of dryland and the countries that fall within the Sahel are all less economically developed countries (LEDCs) which all have rapidly growing populations. Approximately a quarter of the world’s population lives in this dry area.

The Sahel is suffering land degradation which include:

-          Fire

-          Hunting

-          Agriculture

-          Deforestation

-          Tourism

The process begins by fertile land suffering erosion which over time turns to desert. In the Sahel, millions of hectares of land are lost to the desert year on year as a result of droughts and human activity. Pretty hard to imagine unless seeing it for yourself!

This sort of process can have devastating impacts on human life. For example: in 2005 the lack of rain in Niger resulted in the land not being able to support crop growth and as a result nearly 4 million people were subject to starvation. For detailed information on this disaster see: http://www.odihpn.org/humanitarian-exchange-magazine/issue-33/niger-2005-not-a-famine-but-something-much-worse.



Desertification processes



When Britain becomes subject to drought it is nowhere near as extreme as those suffering droughts in LEDCs, so Britain may see an increase in the price for crops, may undergo hose pipe bans and so on, yet we don’t see each other go hungry or famine break out. I think this is an area of importance that students need to consider and be aware of. The droughts in Africa are a whole different extreme to ours.



Desertification processes



A combination of overcultivation, overgrazing, deforestation and climate change is resulting in the Sahel spiralling into desertification. The diagram shows how these causes are resulting in desertification in Nigeria. This sort of diagram can be used by students when considering the actions and results of bad human management with Nigeria being used as another case study. The diagram below is more complex and shows all the possibilities of human actions combined with natural events. These complex diagrams can be combined by students so they make their own diagram that makes sense to them.



Desertification prevention

Anyways back to the Sahel... just because the Sahel is subject to severe drought doesn’t mean it is a lost cause. There are sustainable land management practises that can be put into place to benefit the people and the land, these are: 

-          Tethering live stock to limit their grazing area.

-          Farmers diversifying the types of crops and trees they grow to enhance soil binding, preventing erosion.

      -          Reducing deforestation by cutting back branches on the trees allowing them to grow back
                rather than cutting the whole tree down.

-          Controlling grass burning to small areas to prevent wildfires.

These sort of practises can reverse desertification in some cases.



However, the Sahel is experiencing a new crisis this year (2012), not only is the droughts making peoples livelihoods suffer, a combination of rising food prices and poverty are resulting in a rise in starvation. It is estimated that 16 million people are at risk. For more information, see: http://www.fao.org/crisis/sahel/the-sahel-crisis/2012-crisis-in-the-sahel-region/en/, yet again another case study for students to use/reflect upon.



Links:

http://www.eden-foundation.org/project/desertif.html

http://www.fao.org/crisis/sahel/the-sahel-crisis/2012-crisis-in-the-sahel-region/en/

http://www.fao.org/crisis/sahel/en/

http://desertificationb.tripod.com/id3.html



SAND MOVEMENT

I have discussed previously that desert sand moves by prevailing winds. But there are several ways in which they can move.

Sand particles can be carried by either:

Types of sand movement

Creep – These particles are too heavy to be picked up and moved however they can be slowly rolled by the wind or knocked along the grounds surface when other smaller particles collide with them through saltation.

Saltation – This is the picking up and movement of large particles from the grounds surface. As the winds carry the particles, they pick up velocity causing them to bounce along the ground. This bouncing process can heavily erode surfaces.

Suspension – Where particles are held in the air suspended by upward air currents which are then carried by winds.

Beach dunes

Okay slightly off-topic, beach dunes, also knows as coastal sand dunes, are formed by materials being blown in from the coast over the land. Sand is moved inland via saltation and air pressure between the warm land and colder sea.

I am not sure to what extent coastal dunes relate to desertification processes, however I came across coastal dunes when exploring the different types of dune formations and thought I’d make reference to them as I vaguely remember learning about them.

Unlike desert dunes, which comprise of little or no vegetation, coastal dunes can enhance vegetation growth. There are several sequences for the development of these particular dunes:

• At the back of the beach, sand can become trapped by rocks, seaweed and driftwood. Vegetation struggles to grow here however the little vegetation that does grow are referred to as pioneers e.g. sea rocket and saltwort.
• The development of the first dunes are known as embryo dunes. These dunes become stable by the growth (colonisation) of grasses e.g. sea couch, lyme and marram.



Coastal dune transect

• Embryo dunes can raise in height forming foredunes. These foredunes are mobile and can move up the beaches creating a main ridge (yellow dune), fixed dunes (grey dunes), dune heaths and mature dunes which all support a range of vegetation (see diagram). For more information on these types of dunes, the types of vegetation they support and the processes involved see:

http://www.s-cool.co.uk/a-level/geography/coastal-processes/revise-it/coastal-deposition

http://www.seftoncoast.org.uk/shore_featuresanddune.html

http://www.geography-site.co.uk/pages/physical/coastal/dunes.html

I do believe, however, that I have gone way off topic of ‘desertification’ and have been pulled into coastal environments, which is not an area that is classified under extreme landscapes. Going off topic is an easy thing to do, especially when in the classroom. I may return to coastal landscapes, their processes and features in later posts. For now it is only important that students are aware of the types of sand movement and are able to define each process.

Links:

http://milford.nserl.purdue.edu/weppdocs/overview/wndersn.html

http://geography.howstuffworks.com/terms-and-associations/sand-dune1.htm

DESERT DEPOSITIONAL FEATURES

In terms of the depositional features found in a desert, the majority of links refer to those deserts that are hot and consist of sand and other fine materials.

From what I have gathered, there is only one depositional feature which is sand dunes. Makes sense seeing as there is next to nothing in these deserted lands.

So there may only be one depositional feature that can be found in these regions however there are many types of dunes of which some move and others are fixed:

• Live dunes – These dunes move frequently and their shapes vary. These are dependent on the speed the wind is depositing or removing sands and the size of the materials being transported.     

• And fixed dunes – These dunes tend not to move and their shapes tend not to change. These dunes are secured down by vegetation and opposing winds.

The several types of dunes are:

Barchans – A curved, arc shaped sand mound with horns facing downwind formed in arid regions.

Parabolic – These are U-shaped mounds that form in the reverse direction of a barchans. They consist of sand tails which may hold vegetation

Blowout

Traverse – these are horizontal to the prevailing wind, and form a wave like pattern

Longitudinal – also known as Seif dunes, stretch parallel to the prevailing wind with rounded or pointed tops. These can reach 300m in height and range up to 300km in length.

Blowout – These are most commonly found on beaches, where the winds are travelling in the same direction creating causing a mound of sand to be hollowed out on the windward side of the mound.

Star – These dunes are mounds that are subject to different wind directions, forming their star-like pyramidal structure.

Star dune

Other terms:

Loess – This is the lightest material carried by the winds which form a so-called blanket covering the existing land. This blanket is easily eroded and rain penetrates through them rapidly. 

A useful, detailed website with great examples of deserts and dunes can be found is: http://www.indiana.edu/~geol116/Week11/wk11.htm. This link even covers glaciers as well which may be useful when looking at my older posts.

Links:

http://hrsbstaff.ednet.ns.ca/mcallip/Deserts/desert_deposit_features.htm

http://www.ux1.eiu.edu/~cfjps/1300/deserts.html

TYPES OF DESERT

When you think of a desert what do you think of? Vast areas of land that comprise of nothing but sand and a ridiculously hot climate?

Well this is one of many types of desert. It is correct to refer to a desert as dry, with very little or no vegetation which is inhabitable, however not all deserts are hot.

Polar Desert - Antarctica

I will now discuss the different types of desert:

• Polar and ice deserts, e.g. Antarctica

• Continental interior deserts, e.g. Gobi Desert of Mongolia

• Trade wind deserts (subtropical deserts), found between 30°N (Tropic of Cancer) and 30°S (Tropic of Capricorn) of the equator (between Hadley cells), e.g. Sahara Desert and Simpson Desert.

• Coastal deserts, where cold oceans are located next to hot coastal regions e.g. Atacama Desert and Kalahari Desert.

Coastal Desert - Namibia

• Orographic deserts (rain shadow deserts), located near mountains e.g. Basin and Range of Nevada and eastern Oregon’s deserts.

It must be noted that deserts all have one thing in common, they receive less than 25cm of precipitation a year.

Desert Processes

• Abrasion –the weathering process whereby materials moved by wind/water wear against each other and solid surfaces.

Trade wind desert - The Sahara

• Ventifacts – Large rocks that are subject to erosion by the transportation of sand and ice crystals by the wind.

• Desert varnish – the red to black coating found on exposed rocks in arid regions. These colours are formed by oxides (iron and manganese) that are carried by the wind.

• Desert pavement – the process in which desert winds carry/remove the finer sands in an area leaving the coarser materials behind.

Links:

http://www.tulane.edu/~sanelson/eens1110/deserts.htm

http://www.agc.army.mil/research/products/desert_guide/lguide1.htm

http://www.onegeology.org/extra/kids/earthprocesses/desertTypes.html

http://www.cas.muohio.edu/~rakovajf/WTTW%20Desert%20Varnish.pdf