Geologic Features
| Feature | Description | Picture |
| Columnar Basalt | When basaltic lava flows cool and solidify they contract, often developing fractures perpendicular to their surface. Individual columns tend to have a hexagonal (six-sided) cross section. Since columns are always at right angles to the cooling surface, vertical columns are seen in lava flows and sills, horizontal in dikes, and columns typically radiate outwards from the center of pillow lavas. The hexagonal columns may then become exposed when the lava flow is eroded. |
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| Cinder Cone | Due to the large amount of volcanic activity in Iceland, cinder cones are a common feature on the landscape. A cinder cone is a volcano constructed of loose rock fragments ejected from a central vent. The slope of a cinder cone is much steeper then that of a shield volcano. Most of the ejected material lands near the vent during eruption building the cone up to a peak. Cinder cones tend to be much smaller then shield volcanos. Few of them exceed a height of 500 meters. |
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| Geothermal Pools | The thermal pools of Iceland were definitely a huge hit with the IUPUI travel group. The pools are formed when hot water ascends through narrow channels from deep sources in the crust. The temperature of the hot springs is up to 100°C. The blues and yellows seen in the pools are a result of algae and mineral deposits. Nevertheless, Icelanders know exactly how to exploit this natural resource. Nearly half of the stops on our trip offered some sort of naturally heated pool or steam sauna, a relaxing end to a day of traveling and adventure. |
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| Geyser | Geysers erupt because the
thermal water ascending throuh ther channels boils at some depth
below the surface. As the water boils it flashes into steam, and
as the steam occupies far greater volume than water the water
above in the channel is thrown high up into the air. At about 23
m depth in the Geysir pipe the water is at 120°C temperature. It
is in equilibrium with the pressuere of the water above in the
pipe, i.e. the weight of the water above keeps the boiling down.
At a depth of around 16 m, the temperature of the water sometimes rises above boiling, seen as increased turbulence at the surface. This turbulence (boiling) can increase to the point where the water above in the pipe is lifted slightly, and a chain reaction starts - the pressure decreases making further boiling possible and the water flashes into steam, resulting in an eruption in Geysir. |
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| Glaciers | Today approximately 10% of the
land area of Iceland is covered by glaciers. During the last Ice
Age almost all of the country was covered by permanent snow and
glacier ice. A glacier is a thick mass of ice that forms from
the compaction and recrystallization of snow. Glaciers form in
an area, because more snow falls in the winter than can melt in
the following summer. The accumulation of snow at the head of
the glacier causes the glacier to flow due to gravity. http://www.casdn.neu.edu/~geology/department/staff/colgan/iceland/glaciers.htm |
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| Lava Tube | During long-lived eruptions, lava flows tend to become "channeled" into a few main streams. Overflows of lava from these streams solidify quickly and plaster on to the channel walls, building natural levees that allow the level of the lava to be raised. Lava streams that flow steadily in a confined channel for many hours to days may develop a solid crust or roof and thus change gradually into streams within lava tubes. Because the walls and roofs of such tubes are good thermal insulators, lava flowing through them can remain hot and fluid much longer than surface flows. Tube-fed lava can be transported for great distances from the eruption sites. |
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| Obsidian Flow | An obsidian flow is a dark colored to black volcanic glass usually of rhyolite composition, that is characterized by its conchoidal fracture. In the past it was used for making arrow heads and jewelry. It is formed by quenching a lava flow of rhyolitic composition very quickly, not giving the the flow time to cool slowly and form larger crystals that would normally be seen in a ryholite. As you can see the structure of obsidian is such that it breaks like glass and can also be as sharp as glass. |
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| Outwash Plain | When glacial ice melts, the water moves away from the glacial snout in fast flowing streams and rivers. Large complex braided stream outwash plains are formed when water transports vast quantities of sediment and larger debris. If the sediment load is very large in relation to the velocity of the stream, the more coarse material may start to block the stream, choking it and forcing it to constantly change it's course. The stream starts to diverge, splitting into numerous segments which split and join repeatedly, forming small islands. Braided streams are typically shallow and wide, surrounded by poorly sorted rock debris. |
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| Rift Valley | A Rift Valley is a valley that is created from the separation of continental plates. This is a form of continental drift commonly referred to as a divergent continental plate boundary. The continental plates are being pulled apart by forces from deep within the earth. As these plates are pulled and stretched a rift will begin to form. This rift, when exposed on the surface, is called a rift valley. |
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| Soil Horizons | Soil horizons are different bands of color or changes in composition that lay horizontally in the ground. Soil horizons are formed when there is a change in the form of debris being deposited in the soil record. This could be caused by going from standard erosion and deposition to a deposit of ash from an eruption. This is what is seen above. The black layers are ash layers from volcanic eruptions. |
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| Table Mountain | Reykjavik Energy started in 1990. Here they harness the geothermal heat at Nesjavellir for a hot water supply and power. Power harnessing is done in three phases. First, is the collection and processing of steam from boreholes. Next, steam is conveyed to steam turbines where electricity is generated, and then the steam is used to heat cold water. The harnesses power of Icelands geothermal areas, including Nesjavellir, is about 70 Mwt, and annually about 60 million cubic metres of hot water flow through the distribution system. |
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| Nejavellir | Reykjavik Energy started in 1990. Here they harness the geothermal heat at Nesjavellir for a hot water supply and power. Power harnessing is done in three phases. First, is the collection and processing of steam from boreholes. Next, steam is conveyed to steam turbines where electricity is generated, and then the steam is used to heat cold water. The harnesses power of Icelands geothermal areas, including Nesjavellir, is about 70 Mwt, and annually about 60 million cubic metres of hot water flow through the distribution system. |
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