Write a short article about a major volcanic eruption Essay

Write a short article about a major volcanic eruption - Essay Example Volcanoes are powerful forces of nature. According to Ritter et al., volcanism is simply the manifestation of processes that occur in earth’s mantle on the surface of the earth (1). Rocks and minerals are liquefied into magma in earth’s mantle due to heat produced by extreme pressure. Weaknesses in the earth’s crust allow vents to form that allow magma to escape. This magma can emerge through the crust under the sea or on dry land. These vents will create three possible types of volcanic landforms. The type of landform is dictated by the mineral make-up of the magma that is expelled through the vent (2). Shield volcanoes, such as the Hawaiian Islands are made of magma that has low viscosity. It is mostly basalt and runs like water. Cone volcanoes are made of magma that is high in silica. The magma is sticky so it builds up making the steep sides of a cone shaped mountain. Similar to these are composite cones that are made of magma and ash. They are irregularly sh aped volcanic mountains. A final landform created by volcanoes is called a caldera. This is a huge empty space in the volcanic mountain created by a massive eruption. This is a prominent feature that was created by the eruption of Thera. The Greek island of Thera is located in the Mediterranean Sea just northeast of the island of Crete. The island is known in modern times as Santorini. The geologic shape and structure of the island is typical for volcanic islands in the Aegean and Mediterranean seas. The island was a mixture of ash and silica based materials with gentle slopes near the shoreline rising to an inland, conical peak. Thera had been slowly building for at least a million years. The current arrangement of the small islands of Santorini did not happen with just one eruption. As many as twelve eruptions over the past million years have made Santorini what it is today (3). The eruption that occurred around 1600 BC was,

Discus and Biomechanics Essay Example | Topics and Well Written Essays - 3000 words

Discus and Biomechanics - Essay Example The knees should be moved forward but with flexion in order to provide support for the hands with the discus. The ankles should also be a bit up and with flexion in order to put the hips in position and to provide support to the knees. The hops are help in the front position with no rotation so as to provide the base for the discuss weight on hands. The hands are also placed in a relaxed position on the sides in order not to destabilize the stability. The center of gravity is maintained at the center, in discus throw, one should try to maintain the center of gravity as low as possible in order to provide them with stability as they try to increase the momentum required just before the throw. The left hand that has no discus should always be maintained in the same position with the right hand that holds the discus so that there can be adequate weight distribution across the body. Being with the neck at no rotation helps to keep one’s gaze in front where the discus is to be thro wn. Base Support: standing with the left foot in front of the right foot, the right arm with the discus is put to swing in a forward motion while the left arm remains in a backward swing. The waist in a leftward rotation 33 degree and legs are also spread. Description of Movements: the discus thrower has his right arm with the discus in front while keeping his stance stable. His legs apart with the left leg in front of the right leg and his eyes fixed on the throwing direction as he begins to rotate. This is the second phase where getting a good stance is important. Proper Techniques and Flaws in this Performance: the right arm in front with the left leg, is to spread the body weight so as to increase stability of the discus thrower. The shoulders are allowed to rotate at certain degrees as they should allow the load in the hand to move freely, and by the time the right