Cascadia subduction zone, a fault that runs from Vancouver Island to northern California, is bracing itself for an earthquake as pressure has built up in the zone since the 1700s. The eventual earthquake could measure at a magnitude of 9 and could be potentially comparable to the San Sixto earthquake, which hit Mexico in 1787 with an estimated magnitude of 8.6.
The Cascadia Subduction Zone, or Cascadia Fault, is a convergent plate boundary in California, USA. It has caused the 1700 Cascadia Earthquake and is famous for being the land of ‘ghost forests’.
The Cascadia Subduction Zone stretches from Vancouver Island to northern California. It separates the Explorer, Juan de Fuca, and Gorda plates, on the one hand, and the North American Plate, on the other.
The Cascadia Subduction Zone has been under the watch of geophysicists since the 1980s. They have found similarities between this fault and faults in Chile, Alaska, and Japan’s Nankai Trough. In the 1960s, underground fractures were uncovered by oil companies in Puget Sound. These were believed to be inactive through the 1990sThe Cascadia Subduction Zone is known for causing the 1700 Cascadia Earthquake. At that time there were no written records made. However, legends and anecdotes from the Olympic Peninsula speak of an epic battle between a Thunderbird and a whale. In 2005, seismologist Ruth Ludwin analyzed anecdotes from various First Nations groups and found out that the people were actually referring to earthquakes and saltwater floods. This collection of data allowed her to come to the conclusion that the earthquake occurred in the year 1701.
One day in March 1986, when it was low tide, paleo geologist Brian Atwater dug along Neah Bay using a nejiri gama, a small hand hoe. Underneath the top layer of sand, he uncovered a distinct plant—arrowgrass—that had grown in a layer of marsh soil. This was proof that the ground had suddenly sunk under sea level, causing saltwater to kill the vegetation. The events had happened so quickly as to cause the top layer of sand to seal away any air, thus preserving the centuries-old plants.
Since then, the area has been known as a ‘ghost forest’. Several more were discovered later in 1987 and 1995.
The last known great earthquake caused by the Cascadia Subduction Zone was the 1700 Cascadia Earthquake. Geological evidence indicates that there had been at least 7 great earthquakes in the seismic zone in the last 3,500 years. Who knows when it might wake up again?