Some 250 miles south of Portland, Oregon, Crater Lake is the deepest lake in the United States. However, it did not start this way. It was once the top of Mount Mazama, a supervolcano in the Cascade Range that towered over 12,000 feet above sea level. The transition from enormous mountain to the caldera it is today was explosive: about 7,700 years ago Mount Mazama erupted, emptying twelve cubic miles of lava and enormous amounts of pumice out of its magma chamber in mere days, during an eruption forty times as powerful as the 1980 eruption of Mount St. Helens. The magma chamber then collapsed in on itself, forming the caldera, which filled to form Crater Lake.

Extent of Mount Mazama Ash Cloud Sedimentation

During this explosion, Mount Mazama also erupted an enormous ash plume.This is where archaeology ties in. The ash cloud was so immense that it stretched over nearly the entire northwest, as far north as Alberta, Canada. This ash layer, which soon cooled to a solid, remains an easily visible lighter layer of sediment throughout this whole area, providing archaeologists studying much of the Pacific Northwest with a definitive time stamp for relative dating. This method of dating uses stratifigraphy, which analyzes sedimentary layers and the finds contained within them to determine their dates in relation to each other and learn what the environment was like at the time the layer formed.

The ash layer is visibly lighter in color compared to the surrounding sediment layers

This and other kinds of archaeological survey and dating, mostly Potassium-Argon dating of igneous rocks, have also provided evidence on how Mount Mazama evolved and its development since its most recent eruption. The oldest lava flows from Mount Mazama are 400,000 to 420,000 years old, and in between then and now there are lava flows of varying ages. Mount Mazama itself is made up of many smaller shield volcanoes and stratovolcanoes that, through time, eruptions, and glaciation merged into one supervolcano before its ultimate eruption and collapse. Remnants of the cones of these other volcanoes remain, and geologists and archaeologists can date the lava they erupted to find how Mount Mazama itself evolved.

A diagram of the sediment layers at Mount Bachelor, 100 miles from Crater Lake, shows the stratigraphy of Mount Mazama ash

Studying the volcano itself gives archaeologist valuable context for understanding the cultures of this area. For the Klamath people of Northern California and Southern Oregon, Mount Mazama and Crater Lake are central to their cultural identity and history. They had lived in the area for thousands of years before the most recent catastrophic eruption, and believed Mount Mazama and the region’s other volcanoes to be the home of spirits. In their cultural belief, the eruption happened when the spirit of the underworld broke out, and their culture’s spirit chief forced him back, thus trapping him in the collapsed volcano. The rain that then came to put out the fires filled the crater to form Crater Lake, a sacred site which they kept secret from outsiders until a white settler accidentally discovered it in 1852. For archaeologists, understanding Mount Mazama is critical to understanding their cultural history.

Sources

http://www.craterlakeinstitute.com/crater-lake-news/how-crater-lake-came-to-be.htm

http://www.oregonencyclopedia.org/articles/mt_mazama/#.Vftf14b3arX

http://www.siskiyous.edu/class/geol0830/mazamaguide2013.pdf

http://volcano.oregonstate.edu/crater-lake

Further Reading

The legends behind Crater Lake:

http://oe.oregonexplorer.info/craterlake/history.html#legend

Thundereggs: an incredibly cool geologic phenomenon left behind by Mount Mazama’s eruption:

http://traveloregon.com/trip-ideas/grants-getaways/thunder-eggs-oregon-treasures-in-the-dirt/

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Context is very important to Archaeology. Context is the relationship between artifacts. By looking at the relationships between artifacts, Archaeologists are able to learn about the history and recreate past events. Without context, it is impossible for archaeologists to create an accurate picture of the past. The history of Great Zimbabwe and its people is an example of the need of context to create accurate representations of the past using artifacts.
Great Zimbabwe is the ruins of a city located in the southeastern hills of Zimbabwe near Lake Mutirikwe. Great Zimbabwe was a city that existed approximately between the 12TH AND 15TH AD. It acted as the capital of the kingdom of Zimbabwe. The Zimbabwe civilization was one of the most significant civilizations that existed during the medieval period. The ruins are all that is left of a great trading civilization that existed in the interior of Africa. Zimbabwe controlled most trade throughout southern Africa. The city of Great Zimbabwe acted as a center for the trade of gold and ivory. The site began declining during the 15th century prior to being abandoned around 1450 AD.
The remains of Great Zimbabwe were first excavated by J. Theodore Bent and Cecil Rhodes. When Great Zimbabwe was first discovered, archaeologists did not understand what great Zimbabwe was or why it was abandoned. It was believed that the civilization of great Zimbabwe simply disappeared without a trace. As time passed, more information was discovered about Great Zimbabwe and archaeologists understood the context behind Great Zimbabwe. With more context Archaeologists about Great Zimbabwe, such understanding its role as the capital of the Zimbabwe empire and as a center of trade, it has become possible to develop educated theories about the decline and abandonment of Great Zimbabwe. With context, archaeologists have developed multiple theories explain the reason for the decline and abandonment of great Zimbabwe. Some theorists believed that changes in climate caused the abandonment of Great Zimbabwe. Another theory is that a decline in the abundance of gold and ivory in the area caused a decline in trade, this made Great Zimbabwe less viable as a place for the population to live. Some  archaeologists believe that the decline of Great Zimbabwe was caused by the arrival of Europeans in the African continent disrupting trade.

This Is an aerial view of the Great ZImbabwe Ruins
In the past it was thought that the inhabitants of Great Zimbabwe disappeared and that there was no traces remaining of the civilization other than the Great Zimbabwe ruins. Archaeologists did not conduct studies into populations that lived near the ruins of Great Zimbabwe. When archaeologists began studying the Shona population near the Great Zimbabwe ruins, they discovered that the population knew about the Great Zimbabwe ruins and were actually the descendants of the Great Zimbabwe civilization.

Shona People. Believed to be the descendants of Great Zimbabwe civilization

Great Zimbabwe is an example of the important role context plays in archaeology. Without context, it is impossible to create accurate depictions of the past. Context is what allows archaeologists to turn artifacts into theories about the past.

Further Reading:

http://archive.archaeology.org/9807/abstracts/africa.html

http://www.pbs.org/wgbh/nova/ancient/mysteries-of-great-zimbabwe.html

Sources:

1. http://www.sahistory.org.za/topic/great-zimbabwe-case-study
2. http://www.manuampim.com/ZIMBABWE.html
3. http://exploringafrica.matrix.msu.edu/students/curriculum/m7a/activity4.php
4. http://www.bbc.co.uk/worldservice/africa/features/storyofafrica/10chapter1.shtml

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