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All words in yellow will be defined at the bottom of the page. |
| Introduction |
Crater Lake is known for its extreme blue coloured water and fantastic scenic views. It was formed after the collapse of an ancient volcano, named Mount Mazama. This volcano violently erupted around 7700 years ago. That eruption was 42 times as powerful as the 1980 eruption of Mount St. Helens. The caldera was formed after the top 5000 feet of the volcano collapsed. Following this, lava flows sealed the bottom, allowing the caldera to fill with approximately 4.6 trillion gallons of water from rainfall and snow melt, to create the seventh deepest lake in the world at 1,932 feet. A lava dome soon built up to what is know today as Wizard Island. Today, Crater Lake is part of Crater Lake National Park, a major tourist attraction found in southwestern Oregon, United States of America
 www.nps.gov/crla/
Craterlake & Wizard Island http://encarta.msn.com/media_461538480/Crater_Lake_Oregon.html??partner=orp
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| Parts Of Crater Lake |
http://vulcan.wr.usgs.gov/Volcanoes/CraterLake/description_crater_lake.htm
Crater Lake
The 8x10 kilometer caldera lies in the remains of Mount Mazama, which is part of stratovolcano cluster covering 400 square kilometers, was in the southern Oregon Cascades. Prior to its climactic eruption, Mount Mazama's summit had an elevation between 3,300m and 3,700m (somewhere between 10,000 and 12,000 feet). The mountain was deeply cut into by glacial movement, which left many U-shaped notches found in caldera wall. The caldera wall is made up of the remains of Mount Mazama, which was mainly igneous shield type rock. Around the Lake and lower parts of the mountain, sediments of the old mountain can be found, and in some areas layered together.
www.vulcan.wr.usgs.gov/Volcanoes/CraterLake/Maps/map_mazama_general_geologic.html
http://vulcan.wr.usgs.gov/Volcanoes/CraterLake/description_crater_lake.html
One of the most popular features of Crater Lake is its sparkling blue water. But what makes the water so blue? The dramatic colour is actually from the lakes' great depth, clarity of its water, and the way light interacts with water. Water molecules absorb the longer wavelengths of light better (reds, oranges, yellows, and greens). Shorter wavelengths (blues) are more easily scattered than soaked up. In the deep lake, some of the scattered blue light is redirected back up to the surface where we can see it. Melted snowfall fills the lake, so it is mainly clean.
Sunlight is able to penetrate the waters of Crater Lake to great depths. Researchers using an instrument called a secchi disk can easily determine lake clarity. They simply lower the 8 inch black and white disk into the water, and measure the depth at which the disk is no longer visible from the surface. For most lakes, readings deeper than 100 feet are rare, but on June 25, 1997, scientists recorded a world record clarity reading of 142 feet!!!!
www.nps.gov/crla/student/student.htlm#2
Mount Mazama
Mount Mazama was a large composite volcano constructed by growth of many overlapping shield and composite volcanoes. Mount Mazama rose to an approximate height of 3,700 m (12,000 ft) above sea level. The caldera wall displays the geologic layering of lava flows through time. This layering allows geologists to create a time line and find out when the crater was created. The eruptive magma from the volcano were silica-rich, but as time went on they lowered in silica. Mount Mazama began its climactic eruption about 7,700 years ago, blowing out about 50 square km of magma as pyroclastic materials in a few days. The volcanic ash covered parts of the northwestern states to as far as central Canada. Rare particles of Mazama ash have even been found in ancient ice from Greenland.
The landscape after the eruption was a scene of devastation. Geologists have determined that the collapse of the top was a relatively quick event during the eruption, taking only a few hours or days. The surrounding valleys were partly filled with hot pyroclastic flows. The walls of the caldera were unstable and partly collapsed into the crater. Following the climactic eruption, it took about 250 years of rain and snow fall for the caldera to fill to its present-day lake level. Geological studies show that hydrothermal activities are present at the lake floor today! A chemical study of the lake water indicates that warm water enters the lake from the lake bottom. The water is probably heated by hot rock beneath the fractured caldera floor. Scientists are not certain any magma still remains underground but it is likely that Mount Mazama will erupt again someday, but not anytime soon.
 http://vulcan.wr.usgs.gov/LivingWith/VolcanicPast/Places/volcanic_past_crater_lake.html
Pictures Of How The Lake Formed
Figure A: eruption deposits airfall pumice and ash, blown by winds to north and east.
Figure B: Vent enlarges and eruption column collapses; pyroclastic flows deposit the on north and east sides of the mountain
Figure C: Roof of magma chamber collapses, forming caldera as new vents open above fractures; pyroclastic flows deposit pumice and ash on all sides of Mount Mazama and in valleys below.
Figure D: Caldera has been partly filled with pumice and ash from the eruption shown in C and with blocks of rock from the caldera walls.
Figure E: Crater Lake today.
www.craterlake.wr.usgs.gov/geology.html
Wizard Island
Wizard Island rises 762 feet above the surface of Crater Lake. Following the climactic eruption of Mount Mazama, a small cinder cone and lava flows were erupted within the caldera to form Wizard Island. The island appears on the west side of the lake. This cinder cone is surrounded by black volcanic lava blocks. A small crater, 300 feet (90 meters) across and 90 feet (27 meters) deep, rests on the summit. The crater is filled by snow during the winter months, but remains dry during the summer. The reason why the small Wizard Island crater remains dry and not a small lake is due to the drainage. Crater Lake has hardly any drainage streams, where Wizard Island has many. The Island is seen as a tourist attraction as well a small sancturare for people who paddle the lake and decided to rest.
www.craterlake.wr.usgs.gov/geology.html |
| Quick Facts Of Crater Lake |
Location: Oregon
Latitude: 42.93 N
Longitude: 122.12 W
Height: 2,487 meters (8,156 feet)
Type: Caldera
Number of eruptions in the past 200 years: 0
Latest Eruptions: 4,000 years ago (main Mountain) -- at least 800-900 years ago (Wizard Island)
Present thermal activity: None
Interesting!!??!!:
1) Largest known eruption from Cascade Range volcano
2) Caldera-forming eruption 7,000 years ago
3) Mount Mazama was roughly 12,000 feet in altitude before the catastrophic eruption
4) 7th deepest lake in the world
5) Deepest lake in North America (1,932
6) Phantom Ship - a section of the rock wall around Crater Lake - is the oldest rock found above the surface of the lake (400,000 years old)
http://geopubs.wr.usgs.gov/dds/dds-72/site/phant.htm |
| Definitions |
Caldera - a volcanic crater that has a diameter many times that of the vent and is formed by collapse of the central part of a volcano or by explosions of extraordinary violence
Stratovolcano - a volcano composed of explosively erupted cinders and ash with occasional lava flows
Composite Volcano - is built by alternating eruptions of lava and pyroclastic material. Composite volcanoes, also called stratovolcanoes, form tall conical mountains
Pumice - porous volcanic rock that forms during explosive eruptions. It resembles a sponge because it consists of a network of gas bubbles frozen amidst fragile volcanic glass and minerals. All types of magma (basalt, andesite, dacite, and rhyolite) will form pumice
Vent - are openings in the Earth's crust from which molten rock and volcanic gases escape onto the ground or into the atmosphere
Pyroclastic Flow - is a ground-hugging avalanche of hot ash, pumice, rock fragments, and volcanic gas that rushes down the side of a volcano as fast as 100 km/hour or more. The temperature within a pyroclastic flow may be greater than 500° C
Cinder Cone - is a steep, conical hill of volcanic fragments that accumulate around and downwind from a vent. Cinder cones range in size from tens to hundreds of meters tall.
http://www.m-w.com/
http://volcanoes.usgs.gov/Products/Pglossary/ |
| Conclusion |
Every since Crater Lake has become a National Park on May 22, 1902, millions of people have flocked to see this natrual wonder. The clear blue colour of the water and the location of the lake is what has made this geological scence so famous. Just to imagine what Mount Mazama must of looked like on the day of the catastophic eruption, this huge monsterious mountain exploding in a spectical of fire, lava and smoke. Then, with a defining sound, the top of the mountain collapsing downward creating a massive crater, which would later be known as Crater Lake. Today, the area is a great money maker for the US government, but also a reserve for wildlife. By having the area as a National Park, it allows Crater Lake to remain pure and spectacular for generations and years to come.
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