Today: Chapter 17, part I Earth beneath the Ocean. Study guide. · Techniques of mapping the ocean floor Which parts make up a continental margin, and what is the difference between passive and active margin? · How are submarine canyons formed?
Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.
Earth beneath the Ocean
Earth beneath the Ocean
Methods (modern) Submersibles, Sonar (echoes of sound waves), Drill Ships, Seafloor Observatory
First exploration of deep-sea floor with HMS Challenger (1872-1876)
Passive and active continental margins
= Atlantic type margin
*no plate boundary
*no seismic activity
to 10-20km thick layer
*wide continental margin
= Pacific type margin
*convergent plate boundary
*trenches mark the boundary
of continent and ocean, strong earthquakes
*sediment accumulation few km
*narrow continental margin
Note vertical exaggeration!
See Fig. 17.9
Atlantic: Mid-Atlantic Ridge
Pacific: East-Pacific Rise
3) Mid-ocean ridges
Features of Deep-Ocean basins
30% of Earth’s
NOT ridges, NOT margins
subducted, dominant bathymetric feature of the Pacific Ocean.
Mineral grains from cont. rocks
Marine animal shells, skeletons
Minerals crystallize out of water
3) Seafloor sediments
Transport media include
Rivers, glaciers, and wind.
Most lithogenous sediment
is made up of quartz (SiO2 )
Biogenic ooze contains at least 30% of skeletons from
single celled microscopic algae and protozoa.
Carbonate oozes are only found above the calcium carbonate dissolution depth (CCD). Deeper water is more acidic (has more dissolved CO2) and will dissolve the calcite shells.
world oceans. The distribution follows the relatively shallow
mid-ocean ridge that is above the CCD.
Ancient evaporites (halite, NaCl and gypsum, CaSO4)
on the Pacific Ocean
SEM of the surface
of a nodule, evidence
for microbial mediation
of nodule formation?
Mining of nodules
Contain Mn, Fe, Co, Cu, Ni
(Joint Oceanographic Institutions for Deep-Earth Sampling)
sediment is being deposited
Fireball and fallout, iridium
Impact ejecta, tektites, spherules,
4) Sampling the ocean floor
Sediment core taken with drill-ship Joides Resolution in 1997 off Florida
reveals first complete K-T deposits with meteor-debris