When I think of where I'd like to live a desert isn't really the first place that springs to mind, so I was surprised to learn that around the world more than 300 million people live within deserts. but then as one third of the worlds surface is covered by deserts its going to be inevitable as the population grows.
It must be remembered that all of the desert environments are different, not just boiling sun and sand dunes. However all the desert communities face one big issue, the search for water.
Las Vegas, Nevada
Las Vegas is one of the glitziest cities in the USA, a popular holiday destination for many around the world looking to visit the gambling capital of the USA. Located in the Mojave Desert and with a population of just over half a million residents Las Vegas should not work, a desert water supply would not be able to maintain such a large developed area with an average rainfall of 20cm per year. The introduction of the Hoover Dam . has regulated water supplies which supply Las Vegas and the surrounding areas. The Hoover Dam looks as if it could supply the area with water for years to come, but in actual fact the dam only contains enough water to supply the 29 million homes of the south west for a year.
The Mojave desert also has other uses.
Tourism: The introduction of adventure tourism is perfect within the landscape. The desert environment can be used for off-roading, extreme biking, rock climbing, hiking and rock climbing.
The location is often used with films
The military often use desert areas to test out new air crafts.
The desert to me (even thought I've been there) is a vast landscape where not a lot really happens, this blog will explore how wrong I am.
This is the image which immediately comes to mind when I think desert, high sand dunes, little water and camels.
So what is a desert? A desert is any place which receives less than 10 inches of rainfall a year. Due to the very low rainfall desert regions often lose more moisture through evaporation than they receive through rainfall, this is known as a moisture deficit. Deserts cover more than a fifth of the worlds total land surface and can be found on every continent.
Are all deserts hot?
This is a popular misconception that many people have, the largest hot desert in the world is the African Sahara which can reach temperature up to 50C. There are cold deserts, the Gobi desert in Asia and also Antarctica.
Physical Features
Water Shortage: Water shortage in the desert is not limited to low rainfall. Humidity and consequently cloud cover are also in short supply. This in turn means that the surface, and any living things on it, are continually exposed to direct sunlight, causing intense evaporation of any water faster than the rain can replenish it. Soil: Typically the soil the desert is course, light coloured with a high mineral content. Most desert sand is made of tiny particles of the mineral quartz. Placed under pressure for long periods, grains of sand may stick together, forming a type of rock called sandstone. Groundwater: As the desert only receives a very small amount of annual rainfall there is often a small supply of groundwater. This groundwater is often held in layers of porous rocks which are known as aquifers. Groundwater which is held close to the surface may create an oasis, an area of fertile land where grass, trees and plants thrive. Minerals: The desert is a valuable resource in the hunt for oil and gold. In Australia's Great Sandy Desert miners look for black gold (oil). Countries such as Saudi Arabia have used the deserts store of oil to generate wealth for their countries.
Animal Adaptations
Desert animals are specially adapted to their environments, the obvious animal being the camel which can go for days with no food or water. Animals are also more likely to be nocturnal as the cooler temperatures of the night are more favourable than the scorching daytime desert heat, with many choosing to live underground such as the desert tortoise in the desert of south western USA.
Which is a desert?
As a small starter activity in to the subject for younger years the pictures below could be used to see what the students understand to be a desert and will identify the popular misconceptions. All of the landscapes below are classified as deserts but asking the students to identify features and characteristics could help identify areas which may need to be addressed.
A suggestion to conserve rainforests has been to designate areas national parks or reserves, by 1990 there were 550 tropical national park, however this only accounts for 4% of the worlds total tropical forests. A big problem in the conservation of the rainforest is money, countries such as Brazil know that it is not financially feasiable to keep the entire rainforest, especially when private contractors can offer so much money for the areas of land, but the issue of controlling the clearing of small areas is too hard. A scheme was introduced to offset debts to developed countries in an attempt to stop the destruction of tropical forests. The consumer also plays a part in helping to preserve the rainforest. Since the introduction of sustainable forestry in Amazonia many more retailers are requesting that the tropical hardwoods come from a certified forest management scheme. This allows the customer to know they are not contributing to the deforestation of the rainforest. http://www.economist.com/node/616834 A very useful article on the Amazon rainforest, however parts of it may be a little too in depth.
Class Tasks
Task: A GCSE class could spit in to group of 6 or 8 and have a debate about the deforestation of the Amazon. On one side we have Brazil who need deforestation to occur in order to develop and on the other side the rest of the world who are against deforestation. Point for;
Land will provide money
Land can be used for agriculture to feed an increasing population
It is hard to regulate the contractors from central government
Points against;
We only get it once!
It destroys the natural habitats of hundreads of thousands of species
The local, regional and global consequences would be terrible.
Sustainable development of the Rainforest
Sustainable development means that the needs of the current population can be met without the needs of future generations being compromised. There are several different ways in which governments have attempted to intitate sustainable rainforest development.
1. The process of agro forestry where farmers grow trees and crops at the same time, this is beneficial as the canopy provided by the trees provides shelter and prevents soil erosion. The trees above provide dead organic matter which feed in to the soil providing the crops with nutrients.
2. Using satellite technology rainforests can be monitored to ensure that the guidelines and processes being set out are being followed.
3. Logging can be managed by the process of selective logging, trees are only logged once they reach a certain height meaning that they all have roughly the same life expectancy.
4. Replacing trees which which have been cut down to maintain the canopy. This process is know as afforestation.
5. The education of those who are involved in the deforestation process is equally as important as the above processes. If they understand the consequences of their actions this may affect whether they carry on causing deforestation.
As people are looking to go further a field and to more exotic places on their travels locations such as the Amazon have become increasingly popular. Tourism obviously has an impact on the environment but by taking small steps it can be minimalised. Year Eight : Design a eco tourist lodge within the rainforest. Keep in mind the points which are highlighted on http://www.s-cool.co.uk/a-level/geography/ecosystems/revise-it/managing-the-tropical-rainforest.
The map above could be used as a teaching tool in the introduction to the rainforest. Pupils could be asked to identify the locations of the rainforests across the world and to give possible explanations for this. The rainforests lie in the tropical regions of the world, these areas lie between the Tropic of Capricorn and the Tropic of Cancer. The location of the rainforest on the equator is essential as the sunlight it receives is essential energy source in the process of photosynthesis. This light source is also responsible for the temperature within the rainforest throughout the year, with typical temperatures between 22-33C. This may vary with elevation where temperatures may be slightly cooler.
The layers of the Rainforest
The tropical rainforest is made up of four layers. Emergent Layer: The emergent layer contains giant trees which stand above the canopy layer. These trees receive the greatest amount of sunlight, low humidity and strong winds. Canopy Layer: These trees provide a continuous canopy around 60 - 90 feet from the ground, this is partly due to the branches which are often densely covered in plants. 90% of the organisms which live in the rain forest can be found in the canopy layer. Understory: This section of the rainforest only receives 2-15% of sunlight which fall on the canopy. It is relatively dark and home to many young trees. Forest Floor: This layer receives less than 2% of sunlight as a result very little grows here apart from plants which have adapted to receiving very little light. Fallen leaves and vegetation cover the ground and quickly decompose.
Nutrients of the Rainforest
Most rainforest soils have poor nutrients this is due to millions of years of weathering and torrential rains which have caused the nutrients to become washed out of the soil. As a result of this most of the avaliable nutrients withing the rainforest are found in living plants and animals, when a tree dies in the rainforest organisms will absord the nutrients before they become washed away.
Human Impact on the Rainforest
It is a well known fact that large areas of the rainforest are being felled and deforestation is a major problem facing us today. Here are some causes of deforestation;
Corruption
Unrestricted logging
Increased road networks
Expansion of agriculture
Population Growth
Impacts
When rainforests are cleared we lose much more than just trees. Biodiversity of the area is effected greatly. A number of species are dependent on the rainforest for their survival, as their habitat is located there. These species will be forced to either adapt and live in a much smaller area or to won't survive. It is estimated that one species becomes lost every half an hour as a result of deforestation of the rainforest.
The rainforest provides food, fuels, timbre, medicines and fruits and the loss of these products through deforestation is a real issue. There is also concern for the loss of resources which are yet to be discovered especially medicines as almost a quarter of prescription medication in America is derived from tropical rainforest plants and 2000 rainforest plants have been identified by the US National Cancer Institute as having anti cancer properties.
The rainforest has a huge impact on the environment. The removal of the trees means that the soil will lose the primary source of nutrients and rain water will be able to reach the forest floor, washing out any possible nutrients. The removal of trees would increase run off which can cause flooding downstream. This occurred in Venezuela when unseasonable floods were caused by deforestation in December 1999, up to 30 000 people lost their lives and 400 000 were made homeless.
In regards to climate it can be changed on both an local and regional scale, possibly even global depending on the size of the clearance. At a local scale the albedo of the area will be affected as the dark green of the canopy is removed and replaced by lighter shades. The solar radiation will be able to reach the surface much more easily. The soil temperature will fluctuate as a result, this could be harmful for agriculture as it increases the possibility of nutrient leaking within the soil. On a regional scale deforestation may change surface temperatures and also regional air circulation.
At a divergent boundary a new crust will be created as two plates pull away from each. It may cause the ocean to grow wider. Iceland is a prime example of a divergent boundary as the Mid Atlantic Ridge is located here between the North American and Eurasian plates. The North American plate is moving westward and the Eurasian eastward as a result new crust is created on both sides of the boundary. The new crust creates a rift along the boundary which means that at some point in the future Iceland will seperate and the water of the Atlantic will sill the widening gap between the two plates.
Convergent Boundaries
Here crust is destroyed as on plate slides underneath another, and is then reused in the interior of the Earth as. The area where one plate goes beneath another is known as a subduction zone and at these sites mountains and volcanoes can often be found.
Oceanic-Oceanic Convergence
At an oceanic-oceanic convergence one plate is normally subducted under another forming a deep oceanic trench. They can also result in the formation of underwater volcanoes, the debris and lava from these volcanoes will build up over millions of years until a submarine volcano rises above sea level to become an island volcano. Theses usually create a string of volcanoes called island arcs which have been formed in the same way.
Oceanic- Continental Convergence
When the oceanic plate pushes in to the continental plate it is subducted causing the continental plate to lift upwards and form a mountain range. The oceanic plate will sink in to the subduction trench but the deepest part of the subducting plate begins to break in to smaller pieces which become locked for long periods of time. These can then suddenly move due to the increased pressure and cause a large earthquake which may cause an uplift of the land, sometimes by as much as a few meters.
Continental - Continental Convergence
The boundary where two continents meet head on, neither will become subducted because of the light weight of the continental rock. The crust will instead be pushed upwards or sideways under the pressure. A prime example of a continental-continental convergence is the Asia and Eurasia collision 50 million years ago where the Eurasia plate crumples upwards and overrode the Indian Plate, this lead to the slow formation of the Himalayas and the Tibetan Plateau.
Transform Fault Boundaries
Transform boundaries occur when two plates are moving past each other horizontally, these are usually found along the bottom of the ocean floor. The San Andreas fault in California is a transform fault line which occurs on land, it connects the East Pacific Rise with the South Gorda Explorer Ridge. The fault is approximately 1, 300km long and in places it is tens of kilometers wide, the Pacific plate has been moving past the North American plate for almost 10 million years at an average rate of 5 cm/ yr.
To teach the different types of plate tectonics I thought that it would first be useful to use a world map to locate the seven main plates which make up the crust. Then we could identify the features which occur along the plate boundaries and possibly match these to the specific types of boundaries.
The crust of the earth is not a rigid and immobile structure. Early civilization were aware of this and constructed buildings that would withstand earthquakes, such as the Royal Palace in Crete.
How earthquakes occur
Earthquakes are the result of a slow build up of pressure within the crustal rocks. This pressure will build and then suddenly release which causes parts of the surfaces to experience jerking or vibrations. The point where the pressure is released is the focus, and the point on the surface which receives the worst of the seismic waves is known as the epicentre. The earthquake itself may cause a substantial amount of damage and loss of life but the secondary effects can be just as devastating but may last much longer than the primary damage such as lack of water, spread of disease and loss of homes and economy.
Continental Drift
In 1620 Francis Bacon noted the jigsaw like link between the coasts of South America and the west coast of Africa. Later in 1912 a German meteorologist Alfred Wegener published his theory that at some point a long time ago the continents joined together in a super continent called Pangaea. This landmass later split and various continents started to from.
Plate Tectonics
The crust of the earth is divided in to seven layers with a number of smaller sections. These float on a semi molten mantle which move the plates by convection currents. Convection currents are a result of heat generated by the centre of the earth, the hotter semi molten lava from the core rises to the crust and then cools and returns to the core this creates the currents. There are two different types of plates, oceanic and continental. The continental crust is made up of older, lighter rock which is dominated by minerals rich in silicon and aluminium. Oceanic crust is much younger and has a denser rock type. Its dominant minerals are silicon and magnesium.
Case Studies
MEDC: San Francisco October 1989
At 5:04pm on October 17th 1989 an earthquake occured in San Francisco measuring 6.9 on the Richter scale. The quake only lasted 9 seconds but the quake was devastating for San Francisco. The city lies on the San Andreas fault line where two continental plates are moving past each other in opposite directions (a consrvative plate boundary).
The effects of the earthquake;
- 67 Deaths - 6,000 Homes damaged / destroyed - Damage to infrastructure - electricity / gas and water mains cut - 2000 people made homeless - Upper deck of the Nemitz highway collapsing onto the lower deck crushing people in their cars - A section of the San Francisco-Oakland Bay Bridge collapsing - Fire resulting from gas explosions - Massive economic costs ($4.4 billion)
LEDC: Kashmir 8th October 2005
On 8 October 2005, an earthquake measuring 7.6 on the Richter scale hit the Kashmir region of Pakistan. The earthquake was the result of collision between the Indian and Eurasian plates.
Effects of the earthquake;
Approx. 80,000 people died - 79,000 from Pakistan, 1,400 in Kashmir, 4 in Afghanistan
3.5 million left homeless
380,000 were in need of emergency housing
4,000 households were inaccessible by road due to landslides
2.3 million people were without food for the winter
Disease spread, sourced from people drinking the dirty, contaminated water (this was all they had at the time by means of water)
homeless people died from hypothermia in the mountains (there was little to keep them warm as aid was slow to arrive)
Here goes my first blog! I'm going to look at Glaciers, a subject that I have never covered throughout my time studying Geography. So firstly the all important question . . . What is a Glacier? Glaciers are made up of fallen snow which has over passed the melting of evaporation period this then becomes compressed to create a large area of thickened ice masses (the size of a glacier can vary dramatically, some as large as a football field and some being hundreads of kilometers wide), the process takes place over a number of years. The ice masses have the ability to move and currently glaciers make up almost 10% of the worlds surface, most commonly being located in the Polar regions.
The Global location Glacier Regions
Location of Glaciers
Looking at the map above it is quite clear as to why glaciers would be located within the polar regions with their cold temperatures and abundance of water, however the location of glaciers in Chile and parts of Africa may be a surprise to some people. In these areas there are mountain summits such as Kilimanjaro where the higher up the mountain the colder the temperature which leads to the creating of glaciers. The further down the mountain you move, as temperatures rise the process of albation takes place. This is the process by which ice is lost from a glacial surface through the processes of melting, sublimation or the calving of
icebergs.
How Glaciers effect Land
The sheer size and weight of glaciers suggests that they will impact the landscape in some way. Glaciers are also responsible for carrying broken rock far from its area of origin, something scientists have witnessed globally.
Glacial Erosion
Glacieated Vallys : This is where entire mountain sides are removed by glaciers often leaving steep sheer cliffs. An example is Yosemite National Park in the USA where glaciers left deep valleys.
Fjords: "are long, narrow coastal valleys that were originally carved out by glaciers. Steep sides and rounded bottoms give them a trough-like appearance. Because of glacial erosion on the below sea level land surface, when glaciers finally disappear, sea water covers the valley floor". This type of glacial erosion is common in Norway.
Glaciers and Climate Change
Glaciers are a key tool in understanding how the atmosphere has changed over thousands of years, particularly as the age of the ice caps can vary so much. Scientists have taken samples from a number of different glaciers globally and have studied them to gain information about the past climate of our world. The ice caps contain important information such as trapped air bubbles which can tell scientists about different types vegetation and atmospheric conditions. Using this data scientists can map the expected temperature changes to our atmopshere based on the previous Ice Ages, however there is a problem . . . . .
In recent times glaciers around the world have been retreating at an alarming rate, this is mainly due to events such as the Industrial Revolution and the use of fuel such as petroleum and coal which attribute to the increase in carbon dioxide in the atmosphere and also green house gases. The glacier retreat has been so severe in some cases that glaciers have disappeared altogether.
