Comprehensive Geography notes covering all key content at an A* level. Key case studies students are expected to write essays on are also covered in full, with causes, statistics, and impacts. Diagrams are also fully annotated and in colour.
Acid Rain
CASE STUDY: Drax Power Station – North Yorkshire
Background
Drax power station in North Yorkshire is the largest coal-fired power station in
Europe. It is capable of producing 4000 megawatts of electricity – enough for 4
million people. It burns approximately 35,000 tonnes of coal a day, therefore it
produces a lot of sulphur dioxide (SO2) and nitrogen dioxide (NO2).
Tackling Acid Rain
Drax tackled the nitrogen dioxide by using high-efficiency low NO2 boilers.
To reduce the SO2 in the waste gases special equipment was fitted which
reduced emissions from around 250,000 to 100,000 tonnes per year. This
may sound like it is still a lot, but this proves that there are no instant
solutions. Progress is always in stages and not by dramatic moves. These
units remove 90% of the gases, so they are quite effective.
The Environment Agency set the maximum limit, which the power station
must not exceed.
The unit works by pressing the waste gases from the boilers through wet
crushed limestone, which absorbs the sulphur dioxide and becomes gypsum.
(The gypsum is then used to make plaster board). The relatively clean gas is
then released to the atmosphere. The process needs 1400 tonnes of
limestone a day. Most comes from the Peak National Park in Derbyshire.
NOTE the problem here: If you want to ban all mining in National Parks then
you will have to accept that power stations will pollute the atmosphere even
more. Often a compromise is the answer.
The Effects of Acid Rain
Whole forests are being destroyed – Germany’s Black Forest – 90% of all
Germany’s trees may have disappeared by 2100. The acid rain washes away
valuable minerals such as potassium and replaces them with manganese and
aluminium. The trees do not grow strongly and are killed off by drought or
disease which may follow.
Creatures such as squirrels which depend on the trees or ants that eat the
leaf fall are also reduced in number.
Fish life is threatened as the water becomes more acidic. Sweden suffers
from this despite having low industrial activity – so where is the acid rain
coming from?
Water supplies carry increasing amounts of aluminium. Some scientists have
linked this with Alzheimer’s disease, bronchitis and even lung cancer.
Many famous and long-established buildings are being eaten away by acid
rain. The Parthenon in Athens (2500 years old), St Paul’s Cathedral in London
,(400 years old), have survived years with their fine stonework intact. Since
the arrival of industry, much damage has been done (in the past 150 years).
,
, Case Study of a Volcano: Mount St Helens
Date: Started 20th March // Main Eruption 18th May 1980 at 08:30am (Pacific Standard
Time PST).
Where: Mount St Helens is a peak in the Rocky Mountains (fold mountain range) ‘Cascade
Range’ of North America.
Cause: The mountain range was formed approximately 70 million years ago at a convergent
plate boundary. A minor plate, Juan de Fuca, which is oceanic crust (which is heavier than
continental crust) moving eastwards colliding with the continental crust of the North
American Plate (which is lighter than oceanic crust).
The oceanic crust is forced downwards into the mantle. The increase in temperature
destroys this crust, turning it into magma. Pressure increases in the mantle and the magma
rises to the earth’s surface. This leads to volcanic eruptions.
Type of Volcano: Composite Volcano – A term used by geologists for a steep sided volcano,
often symmetrical cones constructed of alternating layers of lava flows and ash. Composite
volcanoes tend to erupt explosively – posing considerable danger to nearby life and property.
The Eruption
20th March 15:47 1980 – 4.2 Earthquake on the Richter Scale (First sign of an imminent
eruption.
27th March – Mount St Helens spews ash and steam.
Early May – Northern side of the mountain began to bulge by 1.5m a day.
18th May 08:30 – Small ash and steam eruptions were rising from the crater of the volcano.
18th May 08:32 – Earthquake magnitude 5 caused the bulging northern slope to move
forwards and downwards. This became a great landslide of ash, glacier ice, snow and rock to
fill Spirit Lake. The material now mixed with lake water formed a mudflow down Toutle
Valley. This eventually blocked the channel on the navigable Columbia River 60Km away.
18th May 08:33 – the landslide exposed magma in the volcanoes vent. This blast called a
‘nuee ardente’ sent out hot gases, steam, dust and rock fragments at speeds of over
100kph. It felled tress up to 24km away. Every form of plant and animal life was destroyed
within this range.
Rest of the morning – Eruptive column rose more than 20km high. 120Km away in Yakima
ash deposits were 1cm thick. Volcanic debris fell from the column onto the remains of the
northern slope called Pyroclasts. The swirling ash particles created lightning which in turn
started forest fires.
Early 19th May – The eruption stopped. Ash cloud had now spread to the central United
States. Some of the ash encircled the globe within 2 weeks of the eruption.
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