*- The Nonsensical Land -*: volcanoes

let me share some interesting facts for now since I have nothing much to do now and am rather free..this post might get rather boring cos it is gonna be a long long post..haha!think it's better that people who cant read long entries to not read cos it's very long...hahaha!might make you sleep too...hurrr=DDDD

just some fun facts..

let's talk about volcanice eruptions then..haha=PP

the documentary influenced me to want to know more about the volcanic eruptions...

VOLCANOES

What is a Volcano?

It is a mountain that opens downward to a pool of molten rock below the surface of the earth. When pressure builds up, eruptions occur. Gases and rock shoot up through the opening and spill over ot fill the air with larva fragments. Eruptions can cause lateral blasts, lava flows, hot ash flows, mudslides, avalanches, falling ash and floods. An erupting volcano can trigger tsunamis, flashfloods, earthquakes, mudflows and rockfalls.

Why do Volcanoes occur?

Deep within the Earth it is so hot that some rocks slowly melt and become a thick flowing substance called magma. Because it is lighter than the solid rock around it, magma rises and collects in magma chambers. Eventually some of the magma pushes through vents and fissures in the Earth's surface- a volcanic eruption. Magma that has erupted is called lava.

How do volcanoes form?

Deep inside Earth, between the molten iron core and the thin crust at the surface, there is a mantle, a large layer of rock that is largely solid, but flows like plastic. When rock from the mantle melts, it sometimes moves to the Earth’s surface through weak spots in the crust, releasing heat, gasses, and rock--a volcanic eruption. But why does this solid(pyrolitic) rocks melt and come to the surface. Due to the temperature, pressure and the presence of the water, which facilitate the rocks' melting.

As one goes deeper and deeper into the earth, there is increasing temperature with increasing depth. This is because radioactive elements deep within the earth are slowly disintegrating and producing heat. The rock in the earth insulates the heat, so that it accumulates and eventually liquefies the rock insulating it. Only slowly does this heat escape, which leads to the drastic differences of temperature with depth. This difference is referred to as the geothermal gradient. The average geothermal gradient is 2° to 3°C per 100 meters of depth, indicating that heat is flowing outward from inside the earth.

Volcanoes are vents for the explosive escape of some of this heat. Magma is a term referring to a mass of completely or partly molten rock containing the volatile that it acquired at its origin in the upper mantle of the earth. These volatile elements are gases either dissolved in the melt or as bubbles of gas that escape when the rock reaches the surface and solidifies. Volcanoes erupt because magma is less dense than the solid rocks surrounding it in the mantle of the earth. As it nears the surface, the volatile gases expand and boil out of the rock, and this force of explosion propels lava from the vent.

Why do volcanoes erupt in different ways?

Most volcanoes occur on plate boundaries. Plate boundaries are areas where Earth's shifting plates meet or split apart, usually with violent results.

Plate margins that are coming together are called convergent margins, while those that are splitting apart are called divergent. A third type, transform-fault margins, are sliding against each other, going in opposite directions (like those of the San Andreas Fault). Volcanoes can occur on convergent or divergent plate margins or over a hotspot, a spot inside the mantle that heats an area of the plate above it.

Colliding Plates

Along convergent margins, when two plates meet, sometimes one descends, usually of oceanic composition, beneath the other, usually of continental composition, in a process called subduction. As the descending plate is forced deeper into the mantle, parts of it begin to melt and form magma that rises to the surface, often in explosive eruptions. Subduction zones tend to create large, classic, cone-shaped volcanoes called stratovolcanoes, such as Mt. St. Helens in Washington State, or Mt. Shasta in California.

Separating Plates

At divergent margins, plates are coming apart and hot rock forces its way to the surface. Many divergent plate margins are under the oceans, creating long undersea rift zones that fill with lava. In some eruptions at divergent margins, the relatively calm, smooth flow of lava creates volcanoes with gently sloping sides, called shield volcanoes.

Hotspots

Hotspots can also cause shield volcanoes to form. As plates move over hotspots, volcanoes spring up and die down in turn, often creating an island chain. The Hawaiian Islands are the result of a hotspot.

Effects of Volcanic Eruptions

It also causes various kinds of hazards like lava flows, pyroclastic fall depositsm volcanic gases, tsunamis and more but lava flows has been known to have killed small number of people due to the prediction of the volcanic eruption that enaled an evacuation of the people. The majority of damage that were brought about by the volcanic eruption were economic, agricultural and runing the settlements.

There are five gases that are produced by volcanic activity. All of these gases are harmful except for water vapor. These five gases are water vapor, carbon dioxide, sulfur dioxide, fluorine, and chlorine.

Carbon dioxide is one of the main causes of the Greenhouse effect, but there are not significant amounts for the carbon dioxide emitted from volcanic eruptions to contribute to the Greenhouse effect

Sulfur dioxide can have a short-term effect on the weather. A sulfuric acid aerosol can remain in the atmosphere for years after an eruption (Fisher). This aerosol blocks the sun and causes cooler temperatures globally. The sulfur dioxide eventually depletes, but is replenished by each eruption rich in sulfur dioxide.

Fluorine can be a deadly to animals after an eruption. It tends to condense in rain and coat grasses and plants (Fisher). The fluorine is poisonous to animals that eat the fluorine-coated grass and plants.

Chlorine is emitted as hydrochloric acid into the atmosphere. Chlorine destroys the ozone layer that protects the DNA of plants and animals (Fisher).

Water vapor is the only one of these gases that helps society by replenishing the water supply.

The volcano eruptions may seem to cause much damage to the society but there are positive effects too. the negative impacts of the volcanic eruption would seem to have over-powered the positive impacts but there are still positive impacts of the volcanic eruption. It provides with an enriched soil and help in creating earth's early atmospheres and minerals.

Types of Volcanic Eruptions

Plinian Eruptions ( Most powerful eruption)Strombolian-type eruption "Vulcanian"-type eruption