Volcanoes

A volcano can be described as an opening, or break, in a planet's surface or crust, which allows hot magma, volcanic ash and gases to escape from the magma chamber below the surface.

In general, volcanoes are found at converging tectonic plates (two tectonic plates moving towards each other causing one of them to break). One example of this is the Pacific Ring of Fire which has examples of volcanoes caused by convergent tectonic plates coming together. They are also found at diverging tectonic plates (two tectonic plates move away from each other leaving a break in the layer of tectonic plates). One example of this is in the mid-Atlantic ridge whereby two plates are diverging leading to the formation of volcanoes.



Image courtesy of http://mail.colonial.net/~hkaiter/platetectonics.html 



There are many effects of a volcanic eruption; firstly the ash and dust particles thrown up into the air cause significant rainfall, lightning and thunder. This is because the ash particles are good at attracting water droplets due to their dipolar positive charge, therefore attracting the waters dipolar negative charge. Secondly, lahars can form if the erupting material comes into contact with large amounts of rainfall or melting snow, lahars are mixtures of ash, mud and water which can cause fast-flowing mud slides. Thirdly, there are obviously the human effects, many lives can lost and lava flows and lahars can destroy settlements and clear areas of woodland or agriculture, the land affected is often irreversible. In some severe cases, volcanic eruptions can cause large-scale disruption, such as the case in 2010 where the Eyjafjallajökull volcano in Iceland led to flights globally being cancelled.

 However, there are also positive effects; firstly the dramatic scenery created by volcanic eruptions attracts tourists and thus increases economic opportunities in an area. Secondly, the volcanic material can often break down to provide valuable nutrients for local soils acting as a great natural fertiliser increasing crop yields. And thirdly, the heat of a volcano can provide opportunities for the exploitation of geothermal energy which is becoming increasingly important and desirable as countries and companies seek to lower global emissions.

So although the effects of volcanic eruptions are often portrayed as negative by the media, these great natural wonders can have tremendously positive effects on areas and if managed and predicted properly, can prove to be a great source of income and a great source of natural beauty for many worldwide.

Is the Burgess Model still applicable today?

The land-use model (pictured below) is known as the Burgess Model or the Concentric Zone Model and was created by the geographer Ernest Burgess in 1924. But is it still applicable to the growing international cities of today?

Image courtesy of BBC

 

The model, originally based on the city of Chicago, was the first to give the explanation of the distribution of social groups within urban areas. It was designed to show what a typical city is most likely to look like in terms of land use. This model is based on the idea that land values are highest in the centre of a city because competition is high in the central parts of the cities which leads to high-rise, high-density buildings being found near the Central Business District (CBD), with low-density, sparse developments on the edge of the town or city. It can loosely be applied to a city such as London; in general land prices are most expensive in the CBD. This is because of the vast number of passers-by and also the expansive transport network. And in general, the further out of the city you go, the cheaper the land prices, although there are of course exceptions, for example, an area such as Knightsbridge in which the average asking price for a house is £2,443,942 is further out than Holborn but house prices in Holborn are cheaper at £1,535,033.

However, there are limits to the Burgess model:

•The model is now quite old and was developed before transport networks were so prominent in the lives of many people. Car's weren't widely owned and getting around was much harder than it is today.

•The development of the internet and telephone has led to increased business being done through technology, with some companies opting to locate in a cheaper location further out. Furthermore, many people now choose to live and work outside the city on the urban fringe -  this is not reflected in the Burgess model.

•Every city is different. There is no such thing as a typical city. Burgess based this model upon, one city, Chicago and it therefore cannot be applied globally.

So in conclusion, although the model can loosely be applied to most modern day cities, it is very hard to consider this as a precise model of the modern day city and there are now too many factors, independent to each city, that mean it is unlikely another model, of suitable precision, could be created.

The link between deforestation and soil erosion

With an area the size of Costa Rica being destroyed each year, deforestation to create land which can be used for agriculture is a growing problem, it needs to be addressed soon before it’s too late. Here, I will be looking at the effects of deforestation on soil erosion.

A forest will protect the soil lying beneath it from the immediate effects of rainfall as the canopy and other factors help to lower the rate of erosion in this type of environment. This is because the canopy reduces the fall of raindrops, reducing their velocity and therefore kinetic energy.

The forest is also helped by the presence of humus in its soils (see image). Humus is the term used to describe any organic matter that has reached a point of stability, where it will break down no further and might, if conditions do not change, remain as it is for centuries. Humus helps to absorb the impact of the raindrop and is very permeable therefore allowing the rain to infiltrate its soils and be absorbed by the roots which can then help the plants grow. This humus also helps to bind these soils together, reducing the impacts of wetting and water-drop impact

Another factor that increases the stability of forest soils is the large, deep, tree roots that tend to bind soils together, compacting them and increasing the total strength of the soils.

Therefore, we can expect that with an increase in deforestation; there will be an increase in soil loss and erosion. If the land is left bare, then the effects will be more dramatic than if the land were to be covered with crops, which would have similar (but to a lesser extent) effects as forests. Furthermore, the type of ploughing, time of sewing and type of crop will influence soil erosion rates.

It is evident that the effect of humans upon the soils of the earth has dramatically increased the rate at which soil is eroded and lost. In Colorado, USA, rates of erosion over the past 100 years have been at circa 1.8mm per year, whereas in the 200 years before that, rates were between 0.2 and 0.5mm per year, showing erosion rates have increased at a rate of 5x since 300 years ago. In this specific area, it is because of the number of cattle that now use the fields.

This situation is something that cannot be ignored and has to be dealt with soon before the damage to our environment is irreparable.

Humus in soil. Image courtesy of http://cookingrut.blogspot.co.uk/2011/05/gardening-tips.html#!/2011/05/gardening-tips.html

What's caused the UK's recent cold chill?

The rarity of snow in many areas of the UK has caused excitement and chaos amongst all. But what caused the UK's cold chill in January 2013?

It appears that there is a link between the UK's cold chills and the stratosphere. The stratosphere is the second major layer of the Earth's atmosphere, just above the troposphere. The stratosphere has a temperature gradient, so as altitude increases so does temperature.


Image courtesy of http://www.nc-climate.ncsu.edu/edu/k12/.ozonelayer 

 

But how does this affect the cold chills of the UK?

Well, it appears that stratospheric temperatures can have a dramatic effect on temperatures here in the UK. For weeks now, forecasters have noticed that the stratosphere has warmed considerably, and in recent times this has indicated cool temperatures are on the way. Such as in 2009 when a jump in the stratospheric temperature in January led to the UK being covered in snow by February.



However the two are not directly related, every fluctuation in stratospheric temperature does not result in the UK being frozen over and every time the UK is frozen over it is not always due to the stratospheric temperature but there is a link.

The stratospheric temperature is providing forecasters with a powerful tool of which to use when predicting weather conditions, however it can also throw the atmosphere into chaos and lead to very unpredictable weather, making it hard for forecasters to predict the outlook for the next 7 days. So, forecasters are facing a huge challenge. It is not until the effects of sudden stratospheric warming's wear off, that predictions can be accurate again.



Image courtesy of http://www.strudel.org.uk/blog/astro/000927.shtml

 

International Aid

Aid is a form of help which can be in the form of money, machinery, food or people. It is usually heard about after a natural; disaster or war however it also happens on a regular basis as the MEDCs try to boost the economies and reduce poverty and starvation of the LEDCs. Due to the demographics of the world and the uneven distributions of income due to the level of development in certain areas, it is usually the countries of the North such as the UK donating/giving aid to countries of the South such as Chile.

There are a few different forms of aid. They can usually be grouped into around 5 categories.

1. Food aid, for example, cereal, which is usually sent when the more developed countries, HICs (high income countries) or MEDCs (more economically developed countries), have food surpluses so therefore can afford to donate their surplus to the LICs or LEDCs (low income countries or less economically developed countries). It is also due to the fact that some LEDCs cannot produce all the food they need because of the lack of fertilised land to grow crops. So with this form of aid the LEDCs benefit directly from the inefficiency and wastage of the MEDCs.

2. Financial aid, which could be a loan or a grant to help the LEDCs kick-start their economies and help the country to develop and reach its objectives which could be to reduce poverty, or maybe to increase technological development so that they can keep up with the advances in the MEDCs.

3. Volunteers and/or experts, people such as teachers or military personnel. These people will travel to the area in need of aid and help by teaching to raise the educational standards of these areas. This is with the hope that it will increase the employability of future generations and give them the basic skill set of reading and writing.

4. Technical Equipment, such as tractors or medical apparatus, can help the locals of the LEDCs grow crops in the correct conditions or help with possible illnesses that may arise due to the lack of clean sanitation and drinking water in some of the areas requiring aid. 

5. Emergency aid, the type we usually hear about, when food and clothing are sent to countries in response to a war, or an earthquake, or other natural disasters. This type of aid is most vital in helping to save the lives of the people in these areas, without this aid, LEDCs would find it near impossible to recover from natural disasters, such as we saw recently in Haiti, in 2010, when over £1,526,956,768 or $ 2,422,202,996 worth of aid was sent. Be it in any of the above 5 forms.

However, it is not just the government of these countries that send aid. Aid can be sent in 4 ways, and from different places/people. It can be multilateral aid which is where countries send their aid via an international agency such as the World Bank. Or it could be bilateral aid which is where the aid is sent directly from one country to another, for example the UK to Chile. Banks can also give aid as loans however these have to be repaid. One more type of aid is from Voluntary Organisations such as Oxfam - who do not belong to a government, but are instead self-funded and these organisations often give their aid to the areas the official governments don't help.

But, why is it that MEDCs are so keen to give aid? Is it just to help out those worse off than that of MEDCs? Or is it to benefit themselves? Conditional aid is aid that is not free, and has 'strings' attached. For example, the money donated may be 'tied' which is where the money received, has to be spent on goods from the lender. 90% of US aid is tied to buying US goods and services, thus increasing the country’s exports and giving the country a better Balance of Payments figure. It is also that loans given have to be repaid, with interest thereby costing the beneficiary money rather than saving it money.  Aid can often have political strings attached to it as well, with some countries asking to build military bases within some countries receiving aid or maybe asking for political support in the UN.

A good example of conditional aid is when Britain gave over £70million to help repair Sudan's main power station, in Khartoum, that kept braking down. However, many of the parts need to help repair the power station had to be purchased from Britain, even if there were cheaper alternatives available, this is because the aid had 'ties' to British goods. The aid did result in the repairing of the power station and has benefitted Sudan's industrialists and those living in cities and urban areas.

 

Avalanches

With the Ski season around the corner, I thought it'd be good to have a look at avalanches and what causes them.

An avalanche is a rapid flow of snow/ice down a slope. Now this can vary from just a small ripple of snow on a ski slope, to vast volumes of snow and ice rushing down the side of a mountain, with varying consequences. Avalanches are caused by a number of factors:

 1. The recent weather. If a snowstorm has been occurring recently then an avalanche is more probable considering recent snowfall puts extra stress on the already existing snow pack, this is especially dangerous if the snow does not bond with the layers of snow already there. The 24 hours after a major snowstorm is the most critical time as this is when the crust is most likely to give way to the pressure.

2. Temperature change. Small changes in temperature for short periods of time usually do not have an effect on whether an avalanche will occur or not, however, if the change in temperature is substantial or sustained then this can seriously weaken the upper layers of snow, causing an avalanche.  

3. Wind direction. Wind on a mountain usually blows up the windward side and down the leeward side, however, as the wind blows, it picks up snow (on the windward side by scouring the snow off the mountain side) and deposits it on the other side of the mountain (leeward side), this increases the volume and weight of the snow pack on the leeward side which can often trigger an avalanche.  

4. Snow pack conditions. This is perhaps the most important factor when looking at avalanche probability ad slope stability as determining whether the snow pack is bound well or loosely will give an idea of how probable an avalanche is.

5. Vegetation. Lone trees and rocks can often weaken the snow pack significantly triggering avalanches. However, not all vegetation is bad; having lots of trees and rocks can break up the snow pack and also help to stop the avalanche if it begins.



Here is an example of the layers in snow pack. Courtesy of http://www.fsavalanche.org/encyclopedia/layer_snow.htm