Science Tectonic plates

Convergent boundary

2 tectonic plates that move towards from each other.

Divergent boundary

2 tectonic plates that move away each other.

Transform boundary

2 tectonic plates that slide past each other.

Convection currents

Circular movement in mantle caused by magma’s heat increasing and decreasing.

Slab pull

When an oceanic plate subducts under a continental plate and drags the rest of the plate along with it.

Ridge push

When new crust is formed and pushes old crust outwards.

Who proposed continental drift

Alfred Wegener

Who proposed seafloor spreading

Harry Hess

What is continental drift

The theory that all continents were once combined to form a supercontinent called Pangaea.

What is seafloor spreading

The theory that when new crust is formed due to seafloor spreading, old crust shows earth’s magnetic field at the time: normal or reversed.

Magnetic striping

When iron in magma that forms new crust reveals stripes along the seafloor and indicates Earth’s magnetic field.

Fault

A fracture in the Earth caused due to transform boundaries.

Subduction

When a dense, oceanic plate gets pushed under a less dense continental plate.

Mid-ocean ridge

A landmark that forms from divergent boundaries and contributes to seafloor spreading.

What would occur over 50 years at a divergent boundary? (4)

• New crust formation as tectonic plates move apart.

• Increased volcanic activity due to rising magma.

• Slight shifts in landmasses, creating new oceanic crust.

• Possible minor earthquakes from magma movement.

What would occur over 50 years at a convergent boundary? (4)

• Plates collide, causing small mountain building

• Frequent earthquakes, likely larger in magnitude.

• Formation of deep ocean trenches or mountain ranges.

• Volcanic activity may increase if subduction occurs.

What would occur over 50 years at a transform boundary?

• Lateral sliding of plates causes accumulated stress.

• Earthquakes are common; they can be moderate to large.

• No significant change in landmass size, but ongoing strain.