Nature have provided us with fascinating landforms and features. The most often adored landforms are volcanoes. Like the perfect cone structure of Mayon Volcano in the Philippines or Mount Fiji in Japan, people look at their beauty and wonder with great appreciation to nature.
Volcanoes are mountains with a very disastrous nature. Their only […]. Taal Volcano is the second most active volcano found in the province of Batangas. A complex volcano in the middle of Taal Lake and is often called an island within a lake, that is an island within a lake that is on an island as well as one of the lowest volcano in the […].
Mayon Volcano is one of the active volcanoes in the Philippines. According to local folklore, the volcano was named after Daragang […].
Together with the atmosphere and the rotation of the earth on its axis. The earth on which weather moves on has its own effect on the weather. The different landforms like mountains, volcanoes, plains, and the […]. Submit Landform Pictures Login. Earlier eruptions built Mount Scott, which lies east of Crater Lake. As time continued, volcanoes began growing to the west building as layers of lava flows and pyroclastic deposits. The presence of glaciers played a role in growth of Mount Mazama, leaving traces of U-shaped valleys carved on the volcano flanks, some of which were filled in with lava flows.
The summit of Mount Mazama grew to 3, m 12, ft at its maximum elevation. Roughly 30, years ago, the composition, or chemical make-up, of the magma began to change, causing more explosive eruptions of low-density rock and ash.
The climactic eruption of Mount Mazama occurred 7, years ago in a two-phase process. The initial phase began as a Plinian eruption, shooting a column of tephra , or rock and ash, 50 km 30 mi high from a single vent on the northeast side of the volcano.
The massive amount of ejected magma allowed the vent of the volcano to widen, causing the eruption column to collapse on itself and send pyroclastic flows down the north and east flanks. The winds carried material great distances causing widespread ash-fall deposits throughout the Pacific Northwest. The second phase of the eruption introduced the opening of circular cracks, or ring-vents, around the peak.
These cracks acted as a wider dispersion path for a larger volume of magma to escape the reservoir. This sequence of events led to the structure of the central portion of the volcano to collapse in on itself, resulting in an 8—10 km 5—6 mi diameter and 1. The Pinnacles, remains of hot ash and pumice, form tall spires above Wheeler Creek. A close up view of the Crater Lake hoodoos shows a wide variety in the size of the volcanic debris.
The larger fragments are pumice and the fine-grained material is known as ash. Volcanism has continued in the caldera after the climatic eruption of Mount Mazama. Shortly after the formation of the caldera, smaller eruptions formed Wizard Island and a mound of lava flow deposits. Rain and snowmelt began to fill the caldera, with eruptions ejecting enough material to keep pace with the rising water levels through the next years.
The last known eruption took place at the base of Wizard Island 4, years ago, and the volcano has remained fairly quiet, allowing roughly 30 m ft of sediment to accumulate on the lake bottom. An ominous statue of volcanic rock, covered with several varieties of lichen, is part of the Devils Backbone dike which cross-cuts four lava units.
What lies beneath Crater Lake was not explored until the late s and mids. In , a USGS marine geologist was able to use acoustic imaging techniques like CAT scans to map the accumulation of sediments after the caldera formed. Measurements of heat flow led to the discovery of thermal vents in the lake. Further exploration of these vents and the caldera floor took place in during a remote underwater surveying followed by a submersible. Rare particles of Mazama ash have even been found in ancient ice from Greenland.
The airfall pumice and ash covered a total surface area of more than 2,, km 2 1,, mi 2 at least 1 mm fraction of an inch thick. A volume of km 3 mi 3 of the mountaintop had disappeared. Mount Mazama did not blow its top off; it collapsed in on itself. As this enormous volume of magma km 3 , or mi 3 was rapidly removed from the chamber about 5 km, or 3 mi below Earth's surface to feed the climactic eruption, it created a huge void underneath the mountain. Leaving no support for this massive dome, the roof of the magma chamber collapsed, forming the bowl-shape depression known as a caldera.
About 5, to 6, years ago, the accumulation of rain and snow filled the caldera. It took perhaps years for the caldera to fill to its present-day lake level, which is maintained by a balance between precipitation and evaporation plus seepage. Note: The description on this page is a general overview about the formation of Crater Lake. For more in depth studies and technical descriptions, please see the following sites:.
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