For more than 100 years, scientists have sought to unravel the remarkable story of Crater Lake’s formation. Before Crater Lake came into existence, a cluster of volcanoes dominated the landscape. This cluster, called Mount Mazama (for the Portland, Oregon, climbing club the Mazamas), was destroyed during an enormous explosive eruption 7,700 years ago. So much molten rock was expelled that the summit area collapsed during the eruption to form a large volcanic depression, or caldera. Subsequent smaller eruptions occurred as water began to fill the caldera to eventually form the deepest lake in the United States. Decades of detailed scientific studies of Mount Mazama and new maps of the floor of Crater Lake reveal stunning details of the volcano’s eruptive history and identify potential hazards from future eruptions and earthquakes.
Mount Mazama was formed over a period of nearly half a million years by a succession of overlapping volcanoes. The first eruptions about 420,000 years ago built Mount Scott, located just east of Crater Lake. Over the next several hundred thousand years, Mount Scott and other nearby volcanoes became extinct, while new volcanoes grew to the west. Layers of lava flows from these volcanoes are visible in the caldera walls and in landmarks along the south rim of Crater Lake, including
Applegate and Garfield Peaks. During the growth of Mount Mazama, glaciers repeatedly carved out classic U-shaped valleys. Some were filled with lava from later eruptions, while others, such as Kerr Notch and Sun Notch, were not.
By about 30,000 years ago, Mount Mazama began to generate increasingly explosive eruptions that were followed by thick flows of silica-rich lava, an outward sign of the slow accumulation of a large v...
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...west edge of the central platform formed lava tubes or channels that sent lava far out onto the caldera floor.
Later eruptions from a vent in the northern part of the caldera, just south of present-day Cleetwood Cove, built Merriam Cone. The erupting Merriam Cone probably never reached the lake surface. The ever-deepening lake eventually drowned the central platform volcano as well. Only Wizard Island managed to grow high enough to stay above the waterline. The last eruptions at Wizard Island took place when the lake was about 260 feet (80 m) lower than today. All of this activity occurred within 750 years after the cataclysmic eruption. The water level continued to rise until reaching near present- day levels, where it encountered a thick layer of porous deposits in the northeast caldera wall. These deposits stabilize lake levels like an overflow drain in a bathtub.
...e morphed it into the quartzite that is seen surrounding the butte (4). Rocks that undergo this process are called metamorphic rock, which is the same as the rock seen years ago by dinosaurs and other extinct creatures. The quartzite rocks were formerly seafloor sediment that was forced upwards, and then surrounded by lava basalt flows. Once erupted through fissures and floods through out most of the area, lava flow eventually created enough basalt to form a thickness of about 1.8 kilometers (1). All of this basalt flow eventually led to the covering of most mountains, leaving the buttes uncovered. The igneous lava flows and loess is reasons that the Palouse consists of such sprawling hills, and rich soil for farming (2). In result of the lava flows, the Precambrian rock Quartzite was formed. And lastly covered by the glacial loess, which were carried by the wind.
"Geology Fieldnotes - Katmai National Park and Preserve." National Park Service: Nature & Science» Geology Resources Division. 01 Apr. 2005. Web. Feb. 2014.
At the end of the last ice age windblown silt covered the lava and basalt deposits. This silt would go on to create the fertile rolling hills of the Palouse. This soil is more than a hundred feet deep in places. Soon, enough time passed for vegetation to take place and more soil started to form.1 The lava flows would end up damming streams flowing from the mountains; in turn forming the current lakes of the region. Layered between the flows of basalt are sand and gravel deposits that washed down from mountains.1
On May 22, 1915, an explosive eruption at Lassen Peak devastated nearby areas and rained volcanic ash farther 200 miles to the east! This explosion was the most powerful in a series of eruptions from 1914 through 1917. ...
Mauna Loa is located on a hot spot in the Pacific Ocean. It is not near a plate boundary, in fact it is 3,200 km from the nearest plate boundary, and is situated in the middle of the Pacific tectonic plate. This is actually a rarity, as 90% of volcanoes are along a tectonic plate boundary. A hot spot occurs where long, stationary vertical pools of magma rise up and towards the plate. Movement of the tectonic plates above the hot spot created Mauna Loa, along with the other Hawaiian volcanoes. The older Hawaiian Islands were once above this stationary hot spot, but have been carried northwest by the slowly moving Pacific plate. As the plate moves, it carries the previously formed, older, volcanoes with it, creating a trail of younger, new volcanoes behind. The islands are lined up along the Hawaiian Ridge-Emperor Seamounts chain, which is 3,750 miles and includes Kauai, Maui, Oahu and Hawai’i, from north to south, respectively. There are around 80 volcanoes in this chain; most of them underwater, consequently the term seamount refer to submarine volcanoes. Three volcanoes of Hawai’i, Mauna Loa, Kilauea and Loihi seamount, are all currently sharing the Hawaiian hot spot. Although, recent evidence has shown that all three volcanoes use have separate plumbing systems to expel the lava from the pool of magma deep below them. It has also been suggested that Loihi is slowly moving Mauna Loa from the center of the island, thus shifting directly over the hot spot. The closer to the hot spot a volcano is, the more active it will be. The Hawaiian hot spot has laid down layers of lava, building up enormous islands from the ocean floor.
The last eruption of this massive volcano occurred more than 115 years ago in 1884. The eruptions of Mount Rainier produce lahar mudflows which are similar to pyroclastic flows except they contain more water. These mudflows carry debris of volcanic ash and boulders that produce lava flows and have the consistency of concrete flowing down a mountain (C.M. Riley. Lahars can flow up to 100 kilometers per hour and can extend to more than 300 kilometers in distance. Because they are hard to predict, give off little warning signs, and move so rapidly through valleys, lahar slides are considered to be one of the most deadly volcanic hazards.
With the lava flowing at a rate of 800 to 1,300 gallons per second from vents on the east side zone of Kilauea, more than 500 acres of new land have been added to the island since 1938. The eruption of Kilauea still continues to flow at two places in the park. The vent within Halema'uma'u Crater and the Pu'u 'Ō'ō vent.
Miesse, Willian C. "Mount Shasta Geology and History." USGS: Volcano Hazards Program - Mount Shasta Geology and History. College of the Siskiyous Library, n.d. Web. 01 May 2014.
37,600 years ago with dacite and andesite eruptions of pumice and ash. Mudflows were very significant forces in all of St. Helens' eruptive cycles. Starting around 2500 BC eruptions of large amounts of ash and yellowish-brown pumice covered thousands of square miles. This eruptive cycle lasted until about 1600 BC. After 400 years of inactivity, St. Helens came alive again around 1200 BC. This cycle, which lasted until about 800 BC, is characterized by smaller volume eruptions.
On May 18th, 1980, one of the most prominent volcanic eruptions in US History took place in the state of Washington. Mount St. Helens had been dormant for almost 100 years before March 15th. On this day, two months before the eruption several small earthquakes shook the earth. This indicated a magma buildup below the surface, and the first minor event that would lead to one of the greatest eruptions the US has ever known. Following the first set of earthquakes, “Steam explosions blasted a 60- to 75-m (200- to 250-ft) wide crater through the volcano 's summit ice cap and covered the snow-clad southeast sector with dark ash. Within a week the crater had grown to about 400 m (1,300 ft) in diameter and two giant crack systems crossed the entire summit area. Eruptions occurred on average from
Stories about volcanoes are captivating. Myths come in different versions, but all of them are capable of capturing yours, and everybody’s imagination.
The Mauna Loa volcano is located in Hawaii and means "Long Mountain" in Hawaiian. It is a giant, basaltic shield volcano. It is one of the largest volcanoes and mountains in the world and has been called the "monarch of mountains". It has an estimated volume of 9,600 cubic miles and takes up half the land of Hawaii. It extends about 120 km starting from the southern tip of the island to the northern region. It is 97 km (60 miles) long, 48 km (30 miles) wide, and is 8,742 km (28,680 miles) high from the base on the sea floor to the top. The slopes are steeper than 12 degrees and about 4 degrees at the top of the volcano. Mauna Loa formed about half a million years ago and in the middle stages of forming into a shield volcano where lava flows to form a sloped and broad flat domed volcanic cone. Along with Mauna Kea, the Mauna Loa volcano is responsible for the creation of the Hawaiian Islands. Mauna Loa has erupted thirty-three times since 1843 and is known as one of the most active volcanoes in the world today. The last eruption was 1984 and lava flowed within 4 miles of the city of Hilo. This shows that it is dangerous to live anywhere near Mauna Loa and that it poses as a threat to anyone living near it because it has a very high possibility of erupting within a very short span of time. Below is a picture of Mauna Loa taken from a bird's eye view.
channel migration, the eruption of a volcano, the drying of a lake, or the destruction of a
The earliest outcropping volcanic deposits date back to about 25,000 years ago. The lavas observed at a -1125 m bore-hole are about 0,3-0,5 million years old. It is known for the first eruption of which an eyewitness account is preserved, in 79 AD. Geologically, Vesuvio is unique for its unusual versatility. Its activity ranging from Hawaiian-style release of liquid lava, fountaining and lava lakes, over Strombolian and Vulcanian activity to violently explosive, plinian events that produce pyroclastic flows and surges.