(Continued from previous post...)
Personally, I think that Volcanoes are a part of nature. Even though it is dangerous, we cannot remove it. We can only accept its existence and make use of its benefits as much as we can.
Tabitha Chiam
Wednesday, May 19, 2010
Geological explanation of conditions of an erupting volcano
1. divergence plate( north american and european)
2. lies above a hotspot
Monitoring the volcanic activity
1. WHAT?? What about a volcano's activity do we monitor?
- volcanic temperature, water level, lakes, mass movement like rock falls, mud flow and seismicity
2. WHY?? Why do we monitor a volcano's activity?
-Plot geology maps- show changes before a volcano erupts
- Risks- health and death
- tourism, business, flights and daily activities
What materials spew out of the volcano?
- ash, smoke, lava, poisonous gases like carbon monoxide, sulfur dioxide and hydrogen chloride
One symptom geologists could rely on in preparation for an eruption- more powerful earthquakes, animals' strange behaviour, rumbling noise
The 2010 eruption of the Iceland volcano begin on 20 March, this caused many flights to and from Europe to be cancelled, creating the highest level of air travel disruption since World War 2. The second phase started on the 14 April, which resulted in an ash cloud which was estimated to be about 250 million cubic metres.
Tabitha Chiam
The ice-land volcano erruption
Geology of a volcano
The geology of Iceland is unique and of particular interest to geologists. Iceland lies on the geologic rift between the Eurasian and North American plate. It also lies above a hotspot, the Iceland plumes.
Signs of an erruption
Usually before an eruption, there will be an earthquake. There might also be some ash and fumes spewing out of a volcano. Animals, proven to be more sensitive than humans, often behave strangely, for example, chickens not laying.
Why it erupts
The volcano erupts because of the diversion plates diverging.
Monitering volcanic activity
What they look out for
Most geologists look out for volcanic temperature, water level, lakes, mass movement like rock falls, mud flow, seismicity
Why they do so
1)Plot geological maps- show changes before it erupts.
2)Risks-health and death
3)Tourism
4)flights
5)business
6)daily activities
Materials which spew out of a volcano
Ash, smoke, lava, and many other solid liquid and gases. In the gases bit, the spew out mostly steam, poisonous gases escape as well and can suffocate people even before the ash hits them. It depends on how built up the gas is as to how much it explodes. Obviously, molten lava is ejected and so are rocks.
Process of an erupting volcano
Despite the variances in the shape of volcanoes, they all erupt in relatively the same way. The process begins when the pressure on a magma chamber deep below the Earth's surface begins to build up. This building pressure causes the magma from the chamber to be forced upward through a series of tubes or conduits. As the magma reaches the surface, it is thrust through the vents on the volcano, resulting in an eruption.
viviana
The geology of Iceland is unique and of particular interest to geologists. Iceland lies on the geologic rift between the Eurasian and North American plate. It also lies above a hotspot, the Iceland plumes.
Signs of an erruption
Usually before an eruption, there will be an earthquake. There might also be some ash and fumes spewing out of a volcano. Animals, proven to be more sensitive than humans, often behave strangely, for example, chickens not laying.
Why it erupts
The volcano erupts because of the diversion plates diverging.
Monitering volcanic activity
What they look out for
Most geologists look out for volcanic temperature, water level, lakes, mass movement like rock falls, mud flow, seismicity
Why they do so
1)Plot geological maps- show changes before it erupts.
2)Risks-health and death
3)Tourism
4)flights
5)business
6)daily activities
Materials which spew out of a volcano
Ash, smoke, lava, and many other solid liquid and gases. In the gases bit, the spew out mostly steam, poisonous gases escape as well and can suffocate people even before the ash hits them. It depends on how built up the gas is as to how much it explodes. Obviously, molten lava is ejected and so are rocks.
Process of an erupting volcano
Despite the variances in the shape of volcanoes, they all erupt in relatively the same way. The process begins when the pressure on a magma chamber deep below the Earth's surface begins to build up. This building pressure causes the magma from the chamber to be forced upward through a series of tubes or conduits. As the magma reaches the surface, it is thrust through the vents on the volcano, resulting in an eruption.
viviana
Wednesday, May 12, 2010
Iceland Volcanic Eruption 2010 (En Qi)
Hello!
A volcano in Iceland (Eyjafjallajökull) erupted. (O.O) Seismic activity started at the end of 2009 and led to a volcanic eruption of Volcanic Explosivity Index (VEI) 1 on 20 March 2010. The plume of ash from a later ongoing eruption beginning on 14 April 2010 led to widespread disruption of air travel from 15 April, with much of the airspace in Europe closed until 20 April, causing cancellation of most flights within, to, and from Europe.
*WHAT KIND OF VOLCANO WAS EYJAFJALLAJöKULL?*
Eyjafjallajökull was a stratovolcano.
A stratovolcano, sometimes called a composite volcano, is a tall, conical volcano with many layers (strata) of hardened lava, tephra, and volcanic ash. Stratovolcanoes are characterized by a steep profile and periodic, explosive eruptions. The lava that flows from stratovolcanoes tends to be viscous; it cools and hardens before spreading far. The magma forming this lava is often felsic, having high-to-intermediate levels of silica (as in rhyolite, dacite, or andesite), with lesser amounts of less-viscous mafic magma.
Stratovolcanoes are sometimes called "composite volcanoes" because of their composite layered structure built up from sequential outpourings of eruptive materials. They are among the most common types of volcanoes, in contrast to the less common shield volcanoes. A famous stratovolcano is Krakatoa, best known for the eruption in 1883.
*WHAT WERE RELEASED DURING THE ERUPTION?*
Usually lava, rock fragments (such as ash, cinders, etc.) are released. Gases such as water vapour, carbon dioxide and sulfur dioxide are most commonly released as well. Volcanoes also released small amounts of other gases, like hydrogen sulfide, hydrogen, carbon monoxide, hydrogen chloride, hydrogen fluoride and helium.
ALSO:
(TAKEN FROM: http://en.wikipedia.org/wiki/2010_eruptions_of_Eyjafjallaj%C3%B6kull#Volume_of_erupted_material_and_magma_discharge)
"The Institute of Earth Sciences (IES) made a preliminary estimate of erupted material in the first three days of the eruption on 14 April 2010 at Eyjafjallajökull. The erupted products are fragmented material, the majority fine-grained airborne tephra. Eruptive products can be split into three categories along with preliminary estimated erupted volumes:
-Material (tephra) in the ice cauldrons around the volcanic vents: 30 million cubic metres (39,000,000 cu yd)
-Tephra filling the glacial lagoon of Gígjökulslón, carried by floods down the outlet glacier Gígjökull: 10 million cubic metres (13,000,000 cu yd)
-Airborne tephra that has been carried to the east and south of the volcano. Uncompacted tephra fallout from eruption plume: 100 million cubic metres (130,000,000 cu yd)
Total: 140 million cubic metres (180,000,000 cu yd) which corresponds to some 70–80 million cubic metres (92,000,000–100,000,000 cu yd) of magma. The magma discharge rate is about 300 cubic metres per second (11,000 cu ft/s) or 750 t/s. This is 10–20 times the average discharge rate in the preceding flank eruption at Fimmvörðuháls.(First Eruption on 20 March 2010).[85]
The IES updated the eruption flow rate on 21 April 2010 to estimation of less than 30 cubic metres per second (1,100 cu ft/s) of magma, or 75 tonnes/s, with a large uncertainty. IES also noted that the eruption continue with less explosive activity"
*WHAT ARE THE IMPACTS OF THE ERUPTION?*
1. VOLCANIC ASH
Samples of volcanic ash collected near the eruption showed a silica concentration of 58%—much higher than in the lava flows. The concentration of water-soluble fluoride is one third of the concentration typical in Hekla eruptions, with a mean value of 104 milligrams of fluoride per kilogram of ash. Agriculture is important in this region of Iceland, and farmers near the volcano have been warned not to let their livestock drink from contaminated streams and water sources, as high concentrations of fluoride can have deadly renal and hepatic effects, particularly in sheep.
2. RIVER WATER
On 22 March, a flow meter device situated in the Krossá glacial river (which drains Eyjafjallajökull and Mýrdalsjökull glaciers) in the Þórsmörk area (a few kilometres north-west of the erupting location) started to record a sudden rise in water level and in water temperature – the total water temperature rose by 6 °C over a two-hour period, which had never occurred so quickly in the Krossá river since measurements began. Shortly afterward, the water level returned to normal and water temperature decreased as well. It is thought that this rise in water temperature is related to the eruption nearby and is affecting part of the Krossá drainage basin. The temperature of Hruná river, which flows through the narrow Hrunárgil canyon, into which part of the lava stream has been flowing, was recently recorded by geologists to be between 50 °C and 60 °C, indicating that the river has been cooling the lava in that canyon.
3. FARMING
The thick layer of ash that has fallen on some Icelandic farms and pastures at Raufarfell has become wet and compact, making it very difficult to continue farming, harvesting or grazing livestock.
4. EVACUATIONS
About 500 farmers and their families from the areas of Fljótshlíð, Eyjafjöll, and Landeyjar were evacuated overnight, and flights to and from Reykjavík and Keflavík International Airport were postponed, but on the evening of 21 March, domestic and international air traffic was allowed again. Inhabitants of the risk zone of Fljótshlíð, Eyjafjöll, and Landeyjar area were allowed to return to their farms and homes after an evening meeting with the Civil Protection Department on 22 March and the evacuation plan was temporarily dismissed. Instead, the police closed the road to Þórsmörk, and the four-wheel-drive trail from Skógar village to the Fimmvörðuháls mountain pass, but these roads and trails were reopened on 29 March, though only for suitable four-wheel drives. When the second fissure appeared, the road was closed again because of the danger of flash floods, which could have developed if the fissure had opened near big ice caps or other snow reservoirs, but the road was again opened at around noon on 1 April.
~Some positive impacts of volcanic eruptions~
- The created scenery created attracts tourism, which means extra income to an area. (mostly shield volcanoes)
- The lava and ash deposited provides valuable nutrients for the soil, making it very fertile and great for agriculture.
- The high level of heat and activity inside the earth can provide opportunities for generating geothermal energy.
- Volcanoes also provide valuable resources, such as zinc, copper, sulfur, arsenic, and lead.
Done by:
En Qi (30), 1.1
SOURCES:
http://en.wikipedia.org/wiki/2010_eruptions_of_Eyjafjallajökull
http://wiki.answers.com/Q/What_gases_are_released_from_volcanoes
http://wiki.answers.com/Q/What_are_the_positive_impacts_of_volcanoes
Wednesday, April 7, 2010
Monday, March 1, 2010
River Features [En Qi]
Hi! =D
Here's a diagram I found that shows the features of rivers.
If it's a bit small you can open it in a new window and enlarge it.A river can create a lot of features through erosion and deposition along its course. Here are some of the river features...
1) Valley
Valleys created by rivers can be in different shapes, depending on the force of the running water.
-Narrow, deep v-shaped valley
The river flows down a steep slope, and there is a rapid downward erosion. The force of the water then cuts into land and forms a narrow, deep v-shaped valley.
-Broad, v-shaped valley
The river flows down a gentler slope, with less rapids in large bends, and erodes sideways, creating a broad, v-shaped valley.
-Wide valley
The river flows in larger bends on a flat land.
2) Rapids
A series of short and fast falls which are known as rapids are formed sometimes along the course of the river, when the river flows over bands of hard and soft rocks.
3) Waterfalls
A waterfall is a vertical flow of water flowing from a great height, usually found in the upper course of the river.
4) Meanders
Meanders are large bends where the river flows in the middle and lower course.
5) Deltas
Deltas are flat pieces of land formed by layers of sediments deposited over time, and are developed at the river mouth.
There are actually a lot more features formed by rivers, but you can go explore them on your own! :) River features can be very fascinating and beautiful, such as waterfalls. Isn't Niagara Falls amazing?
Some websites you can visit:
Books to check out:
1. Raging Rivers by Anita Ganeri
2. Rivers by Nicola Edwards
3. Earth's Changing Rivers by Neil Morris
<3 qi ="D
Saturday, February 6, 2010
Rivers (features)
Valleys- formed by rivers in different shapes and forms. Eg. steep valleys, broad-shaped valleys, etc.
Rapids- A series of short and fast falls along the course the of a river. They are formed when a river flows over bands of hard and soft rocks.
Waterfalls- A vertical flow of water falling from a great height. It is formed when a river flows over a band of hard rocks overlying softer rocks.
Plunge pools- At the foot of the waterfall, the great force of falling water and the rocks carried by the river cut into the land. A depression at the foot of the waterfall is known as a plunge pool.
Tabitha Chiam
Valleys- formed by rivers in different shapes and forms. Eg. steep valleys, broad-shaped valleys, etc.
Rapids- A series of short and fast falls along the course the of a river. They are formed when a river flows over bands of hard and soft rocks.
Waterfalls- A vertical flow of water falling from a great height. It is formed when a river flows over a band of hard rocks overlying softer rocks.
Plunge pools- At the foot of the waterfall, the great force of falling water and the rocks carried by the river cut into the land. A depression at the foot of the waterfall is known as a plunge pool.
Tabitha Chiam
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