8. On a
Mid-Ocean Ridge - Inside the Rift Valley
On the Ridge
More on Plates
Here you see a map of the mid-ocean ridge
The ridge in the Atlantic is called the Mid-Atlantic Ridge, in the Pacific, it is called the East Pacific Rise, and in the Indian Ocean it is either the Southwest
Indian Ridge, Central Indian Ridge or Southeast
Indian Ridge. There are other smallwer segments of the ridige, such as the Gorda and Juan de Fuca ridges off northern California, Oregon, Washington, and Canada.
we took a undersea voyage to a ridge, we would find that is was formed of a
fairly continuous series of active volcanoes that erupt every 100 to
cruise by researchers from the Hatfield Center of the National Oceanic
and Atmospheric Administration (NOAA) collected the fantastic photographs
the seafloor along a mid-ocean ridge located off Oregon -- we will examine
this ridge in future expedition.
The picture on the left shows
that the mid-ocean ridge is composed of volcanic rocks, freshly erupted
rocks called basalt -- active lava-spouting volcanoes!
The video on the
left shows an underwater hot spring, or a so-called hydrothermal
one of the volcanoes. The NOAA researchers made a journey to the
site of the underwater volcano immediately after it erupted in 1998.
So we first identified ridges in the ocean basins using echo profiler data or multibeam data, then collected rock samples from these features to show that the mid-ocean ridges are
chains of underwater volcanoes and inside these volcanoes, lavas are
erupted that form new seafloor...the volcanoes also belch hot water, which
influences the chemistry of the ocean water (as we will see later in the course).
The valley on top of the
mid-ocean ridge, shown at the left, is called a "rift valley" where the crust of the
Earth splits apart, thereby allowing the rise of molten rock from the
mantle below that ultimately erupts lavas from volcanoes that form the seafloor at the center of the mid-ocean ridge.
Last Updated on
Sept. 22, 2008
a. nonvolcanic undersea mountains
b. isolated mountains on the seafloor
c. long chains of active, undersea
volcanoes, that sometimes erupt, and that extend from one ocean basin to the next