Seafloor
Spreading
Mid-ocean ridges
The mid-ocean ridge is the largest
volcanic feature on Earth. Underwater, the Earth’s crust is spreading creating new
ocean floor and rocks. All this occurs where plates collide. The mid-ocean
ridge is made up of thousands of volcanoes and ridges. Underneath a mid-ocean
ridge, partially molten material rises due to pressure. The melted rock (magma)
eventually cools and forms new oceanic crust. “Dikes” are formed when
magma-filled cracks, flow through, until it reaches the surface. Most dikes are
about 2 meters wide between the magma chambers. Since, the site of mid-ocean
ridges are volcanically active, they are warm. Near these warm areas,
hydrothermal vents are located. Hydrothermal vents support life. Some
ecosystems can only survive at these hydrothermal vents.
Seismic recorders and depth recorders
of the 1950’s led to the discovery of the Mid-Atlantic Ridge. The Mid-Atlantic Ridge is a huge underwater mountain chain
covering the globe over 40,000 miles of it! In some locations the mid-ocean
ridge contained a huge rift, or cleft. These rifts could average up to
20-30 miles. At these rifts, partially molten material (magma) rises to the
ocean floor and cools. After it cools it hardens to form new ocean floor.
Discovering mid-ocean ridges
|
Seismic recorders and depth recorders
of the 1950’s led to the discovery of the Mid-Atlantic Ridge. The Mid-Atlantic Ridge is a huge underwater mountain chain
covering the globe over 40,000 miles of it! In some locations the mid-ocean
ridge contained a huge rift, or cleft. These rifts could average up to
20-30 miles. At these rifts, partially molten material (magma) rises to the
ocean floor and cools. After it cools it hardens to form new ocean floor. |
Juan de Fuca Plate Intro The Juan
de Fuca plate is a tectonic plate subducting under part of the North
American plate. It is located near the Mendocino fault zone and along the
Pacific plate. The Juan de Fuca plate is broke up into three pieces: the
Juan de Fuca plate, the southern Gorda plate, and
the northern Explorer Plate. The Juan de Fuca plate is now one of the last
remains of the Farallon Plate. The Juan de Fuca plate has also formed part
of the Pacific Ring of Fire. Plate System Juan de
Fuca is a sight to behold with its unique characteristics. The Juan de Fuca
plate contains all three types of plate boundaries in just a small area.
The first plate boundary is the subduction zone siding the North American
plate, Gorda and Juan de Fuca plates. The second and third plate boundaries is the divergent/transform zone near the San Andreas fault. The
magnetic band in the Juan de Fuca plate reveals that the plates are turning
in a clockwise motion. The clockwise motion has caused geographical features
of interest. These features were caused by the slow subduction and
environment. Also, erosional conditions had some effect. Seismic
activity caused from the Juan de Fuca plate is rare. A factor of this rare
seismic activity is the spreading near the subduction zone. The crust then
becomes plasticlike subduction plate. The subduction plate is thought to
contain strike and dip angles near the subduction extent. The Juan de Fuca plate system is unique
because of its three plate boundaries. All these close plate boundaries
creates features of the Juan de Fuca plate.
Hydrothermal
Vents
Imagine living in a habitat that
receives not even a speck on sunlight. That habitat is the ocean floor. On the ocean
floor, magma rises, causing the crust to crack and magma seeps out the cracks.
At these cracks, hydrothermal vents are located. Hydrothermal vents is pretty
much, a geyser on the seafloor. These hydrothermal vents continuously spew
super-hot, mineral-rich water that helps an unusual array of animal life, including
Giant Tube Worms.