Plates Move ApartPlates Move Apart

Pages 82-88 (section B)Pages 82-88 (section B)

Divergent BoundaryDivergent Boundary

Occurs where plates move apart. Occurs where plates move apart. – Most divergent boundaries are found in Most divergent boundaries are found in

the ocean.the ocean.

Convergent BoundaryConvergent Boundary

Occurs where plates push togetherOccurs where plates push together

Transform BoundaryTransform Boundary

Occurs where plates scrape past Occurs where plates scrape past each othereach other

Ocean Divergent Ocean Divergent BoundariesBoundaries

In the ocean divergent boundaries In the ocean divergent boundaries are also called spreading centers.are also called spreading centers.

Mid-ocean ridges mark the spot Mid-ocean ridges mark the spot where the ocean floor has been where the ocean floor has been spreading apartspreading apart

Rift ValleyRift Valley

A deep valley formed as tectonic A deep valley formed as tectonic plates moves apart, such as along a plates moves apart, such as along a mid-ocean ridge.mid-ocean ridge.

Mid-Ocean RidgesMid-Ocean Ridges

Mid-ocean ridges are the longest Mid-ocean ridges are the longest chains of mountains on Earth.chains of mountains on Earth.

Mid-Atlantic Ridge is the world’s Mid-Atlantic Ridge is the world’s longest.longest.

Earth’s Magnetic FieldEarth’s Magnetic Field

The Earth has a magnetic North and The Earth has a magnetic North and South Pole- just like a bar magnet.South Pole- just like a bar magnet.

The magnetic North and South Pole The magnetic North and South Pole are not the same as the geographic are not the same as the geographic polespoles

Magnetic ReversalMagnetic Reversal A switch in the direction of Earth’s A switch in the direction of Earth’s

magnetic field so that the magnetic north magnetic field so that the magnetic north pole becomes the magnetic south pole pole becomes the magnetic south pole and the magnetic south pole becomes and the magnetic south pole becomes the magnetic north pole.the magnetic north pole.– Basically the poles switch places.Basically the poles switch places.

Sea-floor SpreadingSea-floor Spreading

The newest rock is closest to the The newest rock is closest to the divergent boundary, the oldest rock divergent boundary, the oldest rock is the farthest away.is the farthest away.

Continents Split Apart at Continents Split Apart at Divergent BoundariesDivergent Boundaries

On land, a On land, a divergent boundary divergent boundary causes a rift valley.causes a rift valley.– Over time the wider Over time the wider

the valley becomes, the valley becomes, it will eventually it will eventually sink below sea level sink below sea level and fill in with and fill in with water.water.

Hot SpotsHot Spots An are where a column of hot An are where a column of hot

material rises from deep within a material rises from deep within a planet’s mantle and heats the planet’s mantle and heats the lithosphere above it, often causing lithosphere above it, often causing volcanic activity at the surface.volcanic activity at the surface.

Hot spots are used as a fixed point that scientist can use to measure the speed and direction of plate movements.