Here\u2019s what you\u2019ll learn when you read this story:<\/p>\n
Even long-lived subduction zones eventually die, and scientists believe they are witnessing the slow death of one in the northern end of the Cascadia subduction zone.<\/p>\n
A new study using seismic data gathered from a 2021 expedition shows this slow disintegration, also known as \u201cepisodic\u201d or \u201cpiecewise\u201d termination, in progress.<\/p>\n
The study provides a fascinating glimpse into the formation of other microplates, which are believed to be the remnants of similar geologic processes.<\/p>\n
From the view of our limited lifespans<\/a>, some things seem absolutely endless. But everything, eventually ends, and that includes the ground beneath our feet.<\/p>\n Continental plates come and go throughout geological ages, diving under each other to their own demise. All of this drama takes place around subduction zones<\/a>, and a team of scientists from universities and institutions around North America may have recently captured the first glimpse of this \u201cdeath\u201d process in action off the coast of the Pacific Northwest, where the Juan de Fuca and Explore plates are currently subducting under the North American plate. The results of the study were published in the journal Science Advances<\/a>.<\/p>\n \u201cGetting a subduction zone started is like trying to push a train uphill\u2014it takes a huge effort,\u201d Brandon Shuck, lead author of the study from Louisiana State University, said in a press statement<\/a>. \u201cBut once it\u2019s moving, it\u2019s like the train is racing downhill, impossible to stop. Ending it requires something dramatic\u2014basically, a train wreck.\u201d<\/p>\n Shuck and his colleagues witnessed this geological derailment thanks to data gathered from the 2021 Cascadia Seismic Imaging Experiment (CASIE21). This high-tech expedition used a 15-kilometer long \u201cstreamer\u201d of listening devices to record the echoes of sound waves produced by the RV Marcus G. Langseth<\/a>. With this data in hand, scientists constructed a detailed map of the faults and fractures along this subduction deep beneath the ocean floor<\/a>.<\/p>\n What they found is that the plates<\/a> don\u2019t collapse all at once, but instead break off piece by piece in a process known as \u201cepisodic\u201d or \u201cpiecewise\u201d termination. \u201cSo instead of a big train wreck, it\u2019s like watching a train slowly derail, one car at a time,\u201d Shuck said in a press statement.<\/p>\n The data revealed massive tears along the Juan de Fuca plate, but the big reveal was a huge break where the plate dropped roughly 5 kilometers. Shuck notes that this piece hasn\u2019t torn off completely, but that its close (in a geological sense\u2014it\u2019ll still take several million years for any of these pieces to break off completely). The team backs up this fracture-driven drama, as earthquake records confirm that some sections are active while others are quiet, likely due to a piece breaking off and the rocks<\/a> no longer being stuck together. Eventually, enough of these events can cause a subduction zone to go quiet completely.<\/p>\n A detailed look at this episodic termination can help solve other geologic mysteries in other parts of the globe<\/a>. For example near Baja California lie fragments of ancient plates, or microplates, which are tell-tale remnants of dying subduction zones.<\/p>\n