Integrated Science (H) Sea Floor Stories Integrated Science (H)

Background The ocean floor has turned out to be an important record of Earth’s history. From observations of the sea floor, we now understand the way tectonic plate diverge, the rate(s) at which plates move, the relative age of the sea floor deposits, the topography of the seafloor, and Earth’s magnetic field orientation over time.

Seafloor spreading is a geologic process in which tectonic plates of Earth's lithosphere move apart from each other due to mantle convection. Heat from the mantle makes the crust more plastic, and as it fractures, magma rises and spills onto the crust. The resulting rock - basalt - becomes new crust. Sea floor spreading creates mid-ocean ridges, as in the Mid-Atlantic ocean, and rift valleys, as in Eastern Africa. ridge rift valley Animation, to 1:16

The magnetism of the sea floor helped scientists to understand the spreading. Magnetic minerals within the magma align with the Earth’s magnetic field. When the magma cools into basalt rock, the pattern of magnetic alignment becomes a permanent record in the rock. mantle magma surface magma cooled basalt rock

claim evidence reasoning Methods Study the data, graphs, and maps of the sea floor on the following slides/your handout Use each graphic to make a claim regarding the sea floor Use the evidence in the graphic to support your claim. Suggest reasoning for the pattern in the data Glue in your copy of the graphic to the lab notebook; record your CER adjacent to it Repeat for all the slides

What is the relationship between rock age and distance from a divergent (ridge & rift) boundary? keep

Describe the average rate of plate movement away from the plate boundary keep

How does ocean depth (surface to sea floor) vary with distance from the rift ? sea level Ocean sea floor Lithosphere million years distant from boundary keep? at plate boundary rift zone

How does the accumulated sediment - weathered rock, remnants of ocean life - vary with distance from the rift/ridge zone? accumulated sediment thickness plate boundary rift zone distance

Scientists also noted a pattern of the sea floor when they looked at the the magnetism of the rocks. What do you notice when you compare the seafloor history east of the ridge with the seafloor history west of the ridge? Meh plate boundary rift zone

Summarize What has the ocean floor taught us about: Plate movement? Rate of movement? The age of seafloor deposits? The topography of the seafloor? Earth’s magnetic field history?

Bill Nye to 6:15 SFCC to 2 min BozemanScience to 3 min Brain Pop Video Recap Bill Nye to 6:15 SFCC to 2 min BozemanScience to 3 min Brain Pop

Atlantic Indian