AIM: Explain the process and the evidence for sea-floor spreading ?

OBJ: Given notes and activity sheet SWBAT explain the process and the evidence for sea-floor spreading with 70% accuracy.

DN: HW Check- Drifting Continents Activity SheetWatch plate tectonics (clipnabber.com)

ACT: Introduction to Sea-floor Spreading (definition & evidence)SubductioniPad (eSpark)

HW: Text, read p.23-29, Complete Sea-Floor Spreading Activity Sheet; Work on Being A Scientist Packet, Interim, Jan 22.

Mid-Ocean Ridges (MOR)Mid Ocean Ridges: submarine mountain ranges found near the center of the world’s oceans; site of sea-floor spreading, divergent motion, and newly created oceanic basaltic crust.

Mid Ocean Ridge

Sonar Data of Mid Ocean Ridge

Iceland: Mid Ocean Ridge on land

Iceland: Mid Ocean Ridge on

land

Seafloor Spreading http://geomaps.wr.usgs.gov/parks/animate/A48.gif

Seafloor Spreading: the process by which the seafloor moves apart along both sides of the mid-ocean ridge as new crust is being added. As a result, the ocean floor moves like a conveyor belt, carrying the continents along with them.

Evidence for Seafloor Spreading1] Eruption of molten pillow lavas and smokers (videos): repeatedly occur along the mid oceanic ridge

2] Magnetic Polarity Reversals (videos): Earth’s magnetic field reversals are recorded in ocean crustal rocks and the magnetized stripe patterns are the same on both sides of the ridge.

3] Ages of the rocks: youngest at the ridge and the farther away from the ridge, the older the rocks are.

Subduction (video)Subduction: the process by which the basaltic ocean crust (heavy, dense) sinks beneath the deep oceanic trench and back into the Mantle.

Trench: deep underwater canyons; site of convergent plate boundaries.