What is a core?
A core is a sample of the earth's layers obtained by drilling
into the crust - along continents and the seafloor. Extracting
cores from the seafloor is particularly challenging but offers
new opportunities for obtaining deposits containing relatively
undisturbed sediments. Seafloor sediments and rocks are immune
to many of the erosional forces that scour and redistribute deposits
on land, making their records of environmental history and Earth
processes unique and exceptional.
(Reference: "One Core At A Time," Earth Scientist Volume
XXI, Issue 3 2005)
Who collects cores?
An international partnership of scientists, researchers, and universities,
known as the Integrated Ocean Drilling Program (IODP), was organized
to explore the evolution and structure of the earth. Since
1985, the program's research vessel, JOIDES Resolution,
has collected cylindrical cores of sediment and rock by lowering
instruments into drill holes along the seafloor. By studying
the cores, scientists gain a better understanding of Earth's past,
present, and future.
What this core tells us...
This core, collected from a hydrothermal
mound near the Mid-Atlantic Ridge in 1994, showed for the first
time that hydrothermal ores are deposited both above and below
older sediments. Before Leg 158, scientists thought that these
brecciated (coarse grained with angular rock fragments) ore deposits
formed by tectonic deformation; however, study of this core showed
that this brecciation is not caused by tectonic forces but occurs
in place, greatly increasing our understanding of these important
ore deposits.
Download a jpg of the core. (right-click
to download, jpg: 550KB)
See http://www-odp.tamu.edu/publications/leg_ndx/158ndex.htm for
more detailed information about Leg 158.
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