Sunday, March 16, 2014

A Tale of Two Tuff Cones

View of the reef
Diamond Head Crater
  The Hawaiian islands are amazing places for geologists to study. The islands are all volcanic, and formed over a hot spot in the middle of the ocean thousands of miles from the nearest land mass. These huge shield volcanoes are eroded over time and become weathered green peaks like those seen on Kauai and Oahu. Sometimes after the main shield forming eruptions have ceased, these volcanoes go through a rejuvenation eruption. These resurgent events formed some of the most well known formations on Oahu. Diamond Head and Punchbowl Crater are two formations that occurred a million years after the main volcano of Ko'olau became inactive. And both are examples of tuff cones, formed when fissures opened up under the reef which allowed magma to come into contact with the shallow ocean water. This built up steam which resulted in a huge explosion, sending pumice, ash, and limestone thousands of feet up.

Diamond Head Summit
The particulate then fell back down around the vent creating almost perfect circular caters. Diamond Head housed a military base from 1906-1960's, while Punchbowl Crater became a military memorial cemetery.

Entering Punchbowl Memorial Cemetery
  Both craters tower above the city scape around them, and both provide a bastion of peace inside their walls. From on top of their rims you can easily spot the other crater looming in the distance. It is a sobering reminder that you can never know all there is to know about volcanoes and if or when one might erupt again.

Punchbowl Cemetery, home to 38,000 soldiers killed during WWI, Korea, and Vietnam

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