Tectonics: human imapct and management

Earthquakes impact humans in many different ways and it is probably fair to say that people in LEDC suffer more than MEDC's. Potential impacts include:
1. short-term (immediate) impacts
2. long-term impacts
3. social impacts (the impact on people)
4. economic impacts (the impact on the wealth of an area)
5. environmental impacts (the impact on the landscape)

A way in which the impacts could be studied would be to try to think of the impacts and then consider actual case studies. Students can look at the severity of the impacts comparing LEDC and MEDC's.

The following information is taken from the BBC web site and is a concise summary of the general effects.

Short-term (immediate) impacts People may be killed or injured. Homes may be destroyed. Transport and communication links may be disrupted. Water pipes may burst and water supplies may be contaminated.

Economic impacts:Shops and business may be destroyed. Looting may take place. The damage to transport and communication links can make trade difficult.

Environmental impacts: The built landscape may be destroyed. Fires can spread due to gas pipe explosions. Fires can damage areas of woodland. Landslides may occur. Tsunamis may cause flooding in coastal areas.

Long-term impacts Social impacts:Disease may spread. People may have to be re-housed, sometimes in refugee camps.

Economic impacts:The cost of rebuilding a settlement is high. Investment in the area may be focused only on repairing the damage caused by the earthquake. Income could be lost.

Environmental impacts:Important natural and human landmarks may be lost.

Generally the effects of an earthquake are more keenly felt by a LEDC's than a MEDC's for numerous reasons and the student can try and think about the differences in the 2 that might contribute to the differential. These will include;
1. Communication systems may be underdeveloped, so the population may not be well educated about what to do in the event of a volcanic eruption or an earthquake.
2. Construction standards tend to be poor in LEDCs so building suffer more damage.
3. Buildings collapsing can cause high death tolls.
4. Evacuation and other emergency plans can be difficult to put into action due to limited funds and resources.
5. Clearing up can be difficult. There may not be enough money to rebuild homes quickly and safely. Many people could be forced to live in emergency housing or refugee camps.

Students can apply difficulties to case studies such as the quake in Japan 1995 (MEDC) and the recent quake in the South Pacific (LEDC). Comparisons can be made as to death tolls, building destroyed, those left homeless, the re structuring costs, spread of disease and aid provided to name but a few.

Tectonics: Earthquakes

Earthquakes are one of the most frightening and power natural disasters.
They occur along tectonic plate boundaries in the same way of volcano's. As the plates move pressure in the earth builds and the tension is released via earthquakes. This map shows the global position of the plates.

The area in the earth where the earthquake starts is called the focus or the hypocentre. The centre of the quake on the surface is called the epicentre. I have previously considered the merging of coming together of plates in the blog entitled 'plate tectonics' (not unsurprisingly!) so i am just going to look at the measuring of quakes, the types and then the effects in the next blog.

The machine used to record the power of an earthquake is a seismometer and the value that is placed is assigned under the Reciter scale, the higher the score on the scale the more serious the earthquake. Low score quakes can occur frequently on certain boundaries, with limited damage.

There are 2 types of earthquake with different types of waves of energy. The first is when the waves create a rolling up and down motion called Rayleigh waves and Love waves that cause the ground to twist from side to side. There are earthquakes that occur on land and out at sea and it is the latter that then lead to a tidal wave AKA a tsunami. As well as the initial quake there are also aftershocks that may not be as powerful but can be devastating.

When looking to teach this subject there are many recent examples of severe earthquakes e.g.China's south-western Sichuan province in May 2008 measured 7.8)and tsunamis e.g. Thailand on December 26, 2004. Consideration of the cause/origins and human consequences should bring the subject to life and make it very memorable.

Volcanic processes and Landscapes

We need to look how and where a volcano is formed. They occur on land and under the sea on constructive and destructive plate boundaries. They emit magma that as it hits the surface becomes lava. At the plate the pressure under the crust builds and finally breaks through the surface in the form of a volcano.

Volcano's are frankly awesome given their power of construction and destruction. There are features of a volcano that can be taught by diagram form and annotating. Enchanted learning has a great example. Students need to know the components that are listed below.

ash cloud - an ash cloud is the cloud of ash that forms in the air after some volcanic eruptions.
conduit - a conduit is a passage through which magma (molten rock) flows in a volcano.
crust - the crust is Earth's outermost, rocky layer.
lava - lava is molten rock; it usually comes out of erupting volcanoes.
magma chamber - a magma chamber contains magma (molten rock) deep within the Earth's crust.
side vent - a side vent is a vent in the side of a volcano.
vent - a vent is an opening in the Earth's surface through which volcanic materials erupt.

These can then be inserted onto the diagram below


There are 2 types of volcanoes: Shield (constructive) and Composite (destructive). They look difference and have different effects.

Shield volcano Shield volcanoes are usually found at constructive or tensional boundaries.They are low, with gently sloping sides and formed by eruptions of thin, runny lava. Eruptions tend to be frequent but relatively gentle.

Composite volcano Composite volcanoes are made up of alternating layers of lava and ash (other volcanoes just consist of lava). They are usually found at destructive or compressional boundaries. The eruptions from these volcanoes may be a pyroclastic flow rather than a lava flow. A pyroclastic flow is a mixture of hot steam, ash, rock and dust. A pyroclastic flow can roll down the sides of a volcano at very high speeds and with temperatures of over 400° C.

Many of the syllabuses in schools suggest a case study, I have seen the Mount St. Helens in a MEDC via video, Google Earth and annotation, each method brought the example to life. There are others such as Chances Peak, Montserrat, 1995-97 – an LEDC.

Tectonics: Plate tectonics

Before looking at plate tectonics we should first consider the structure of the earth. In the centre is a solid core. Surrounding the core is the inner core, then the mantle, which is covered in the earths 'skin' or crust.

The temperature of the earth reduces from the core (hottest) to the mantle and then the crust that is either continental crust (carrying earth) or oceanic (carrying water). The crust is made up from plates. the plates move with via the convection currents cause by the radioactive break down of the earths core. This movement is called Plate tectonics . It is plate tectonics that cause the creation of volcano's and earthquakes at a point where the plates meet. the diagram below shows the earth plates.

The plates have moved over many millions of years to form the continents as they currently exist.
The Earth's plates move in different directions

Plates behave differently at different plate boundaries:
1. At a tensional, constructive or divergent boundary the plates move apart.
2. At a compressional, destructive or convergent boundary the plates move towards each other.
3. At a conservative or transform boundary the plates slide past each other.

Tensional/Constructive Margins plate boundaries occur when two plates move away from each other. This allows magma to come to the surface, which hardens into ingenious rock. This can occur over a long period of time but eventually a volcano can develop.

At a compressional or destructive boundary the plates are moving towards each other. This usually involves a continental plate and an oceanic plate. t occurs when a occur when an oceanic plate is forced under (or subducts) a continental plate. as the plates are pushed together they are force upwards causing fold mountains, such as the Alps in Europe.




Conservative (transform faults) plate boundaries occur when two plates slide past each other.






Collision plate boundaries Collision plate boundaries occur when two continental plates move towards each other.





The movement of tectonic plates creates dramatic volcanic eruptions and earthquakes over which the human world has no control, although attempts have been made to manage the effects obviously not the causes.

Extreme lanscapes: Periglacial landforms

Many periglacial landforms are at ground level and can be symmetrical with geometric shapes. The causes of the landforms are often not clear apart from the obvious that they have been generated by one of the processes discussed in the previous blog.

One of the landforms with what i think is a great name is a Pingo. It is an ice core hill.
The Pingo in this picture is in Canada. They generally have a curved top with ice in it, that can melt. Pingos can continue to grow due to the freeze thaw bringing sentiment to the surface.





Ice-wedge polygons are fantastic natural phenomenon and an example of patterned ground. The ones in this picture are found in Hudson Bay Lowlands, Manitoba Canada. The Brown polygons mark the location of massive ice wedges that extend from the surface down to 2 or 3 m.



Plasas are smaller hills of segregated ice and peat. It develops as the vegetation growing in the peat is forced up by the segregated ice underneath so that they die just leaving the pert mound.




The true understanding of the development of some landforms is still debated but they are an interesting contrast to those formed by glacier and rivers. Students could be asked ion a test to distinguish landforms of all 3 landscapes. Contrasting allows them and the teacher to reflect on the learning that has taken place and if certain subjects needed to be revisited.

Extreme landscapes: Periglacial processes

There are 4 main processes that I am going to look at, with the help of the fantastic PhysicalGeography.net web site.

Weathering
This is essentially the freeze and thaw that causes large fragments of rock to be fractured from the main body of rock as the water crystallises, expanding its volume and pressure in gaps and seems in the rock.

Ground Ice
The most common form of ground ice is pore ice. Pore ice develops in the pore spaces between soil and sediment particles where liquid water can accumulate and freeze.

Ice wedges are downward narrowing masses of ice that are between 2 to 3 meters wide at the base and extend below the ground surface up to 10 meters. It is believed that they form when a seasonal crack in the ground forms in the winter. The diagram below shows the process:


Mass movement
The are different types of mass movement including Solifluction which is the downward movement of soil particles that are saturated. the slope does not have to be steep for this to happen. Also Frost creep which is the movement of similar soil and sediment but this is caused by frost freezing and melting. Particles move slowing through this process and gravity. Another type is rock falls as periglacial environments are harsh soil does not deposit easily and there is a lot of bare rock that is exposed the the harshness of the weather causing cracking etc causing the rocks to become unstable.

Erosion
Processes of erosion and deposition in periglacial parts of the world tend to have their own unique character. These characteristics are related to the importance of freeze-thaw action, the presence of strong winds, and the fact that the warm season is very short.

The landforms that have developed due to these processes are remarkable in character and will be discussed in the next blog. Understanding these processes could be contrasted with the processes of the riparian environment.

Extreme landscapes: Periglacial, general

A periglacial environment is one that can be located next to a glacier and therefore influenced by permafrost, freeze/thaw. But permafrost also exists in areas that are not associated with glaciers and so the definition can be extended.

Permafrost is a condition where a layer of soil, sediment, or rock below the ground surface remains frozen for a period greater than a year. Permafrost is not a necessary condition for creating periglacial landforms. However, many periglacial regions are underlain by permafrost and it influences geomorphic processes acting in this region of the world (PhysicalGeography.net). Permafrost land covers 25% of the non glacial land surface.

Permafrost can be very thick but generally it is the first 1 to 3 meters of it that can be subject to a thaw in the summer months. Almost 50% of Canada is covered in permafrost as can be seen from the diagram below:

In the next couple of blogs I will look at the periglacial processes and landforms.