Hello, fellow travelers!
This week I visited the West Coast of the USA to observe the Juan de Fuca plate. It is a relatively small
tectonic plate, I learned, located between the Pacific plate and the North American plate. The Juan de
Fuca plate formed as a result of the Farallon plate breaking up into a series of smaller plates during the
Oligocene. The plate is currently being subducted underneath the North American plate, a process in
which oceanic lithosphere plunges into the mantle along a convergent boundary. Since the two plates are
coming together, or converging, the stresses involved in this case are compressive, resulting in reverse
faults. Because oceanic crust is more dense, it slides beneath the continental crust. The oceanic plate
subducts into a trench, resulting in earthquakes. Melting of mantle material causes earthquakes at the
subduction zone. Juan de Fuca’s plate activity has formed the Cascade Range, the Cascade Volcanic Arc,
and the Pacific Ranges from British Columbia to northern California. Moving north to south down the
Cascade Range, the composition of the rock formed from volcanoes becomes increasingly basaltic.
These geological locations are part of Pacific Ring of Fire, an area where many of the world’s volcanoes
and earthquakes occur. Some ocean-floor sediments are carried down into the subduction zone where the
heat pressure turn them into metamorphic rocks, such as those forming the foundation of the North
Cascades. When the colliding plates cause molten rock to reach the surface, volcanoes form and create
igneous rock. In southern Washington’s Cascade Mountains, Mount St. Helen is notorious for it’s 1980
eruption, where magma deep within the subduction zone violently erupted. The Juan de Fuca plate has
itself broken into three pieces since Farallon’s original fracture: the Gorda plate and the Explorer plate.
tectonic plate, I learned, located between the Pacific plate and the North American plate. The Juan de
Fuca plate formed as a result of the Farallon plate breaking up into a series of smaller plates during the
Oligocene. The plate is currently being subducted underneath the North American plate, a process in
which oceanic lithosphere plunges into the mantle along a convergent boundary. Since the two plates are
coming together, or converging, the stresses involved in this case are compressive, resulting in reverse
faults. Because oceanic crust is more dense, it slides beneath the continental crust. The oceanic plate
subducts into a trench, resulting in earthquakes. Melting of mantle material causes earthquakes at the
subduction zone. Juan de Fuca’s plate activity has formed the Cascade Range, the Cascade Volcanic Arc,
and the Pacific Ranges from British Columbia to northern California. Moving north to south down the
Cascade Range, the composition of the rock formed from volcanoes becomes increasingly basaltic.
These geological locations are part of Pacific Ring of Fire, an area where many of the world’s volcanoes
and earthquakes occur. Some ocean-floor sediments are carried down into the subduction zone where the
heat pressure turn them into metamorphic rocks, such as those forming the foundation of the North
Cascades. When the colliding plates cause molten rock to reach the surface, volcanoes form and create
igneous rock. In southern Washington’s Cascade Mountains, Mount St. Helen is notorious for it’s 1980
eruption, where magma deep within the subduction zone violently erupted. The Juan de Fuca plate has
itself broken into three pieces since Farallon’s original fracture: the Gorda plate and the Explorer plate.
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