the sea floor
seafloor
• water covers 70% of Earth’s surface
seafloor
• deep seafloor largely
unknown prior to 1950’s
seafloor map from Dana (1894)
seafloor
• oceans originated mostly from volcanic de-gassing of water vapor from Earth’s interior
studying the seafloor
direct methods or methods we can see
• rock dredges
• sea floor drilling
• submersibles
indirect methods or methods we cannot see
• sonar
• seismic reflection profiling
rock
dredges
direct
methods
sediment
corer
direct
methods
sea floor
sediment
core
JOIDES Resolution (1990’s-being overhauled)
DSDP (Deep Sea Drilling Project); ODP (Ocean Drilling Project)
…IODP (Integrated Ocean Drilling Project)…
mining the ocean floor
sonar
(sound navigation and ranging)
•sound sent from ship, bounced off sea floor, and recorded at ship
indirect methods
distance to seafloor is calculated from speed of sound in water multiplied by time to get return signal divided by two (wave goes down and up)
known for a long time that sound travels through water
1822 attempt to determine speed of sound in water
indirect methods
sea floor was critical in development of plate tectonics
yellow lines are plate boundaries
seafloor, continents, and plate boundaries
Age of the sea floor in millions of years…
Sometimes there are plate boundaries at
Sea Floor Trenches(plates converge)
mid-ocean ridge (plates diverge)
mid-ocean ridge- conveyor belt
• Volcanoism
mid-ocean ridge
• high heat flow and small, shallow earthquakes
Magnetic Stripes
Ocean Trenches and Subduction