9th grade science unit 2

Seafloor spreading-Process

Magma rises at mid-ocean ridges, cools to form new oceanic crust, and pushes older crust away

Seafloor spreading-Features

Mid-ocean ridges, rift valleys, symmetrical magnetic stripes

what causes Seafloor spreading

Convection currents in the mantle

Seafloor spreading- results

Creation of a new ocean floor.

Convection currents 

Heat from earth’s core causes mantle material to raise and fall

Ridge push

Gravity pushes newly formed crust away from mid-ocean ridges

Slab pull

Sinking of a cold,dense plate pulls the rest of the plate along

Oceanic Plates

Thinner,denser,basalt composition

Continental plate

Thicker,Less dense,Granite composition

Folds

Anticline: Upward arch. Syncline: Downward trough

Faults

Normal Fault: Caused by tension, hanging wall moves down.

Reverse Fault: Caused by compression, hanging wall moves up. Strike-Slip Fault: Caused by shearing, horizontal movement.

Appalachian Mountains

Formed by continental convergence

What are volcanoes

openings in the earth’s crust where magma escapes

Where are volcanoes 

Plate bounderies

Warning signs for a volcano

Earthquakes,Gas emissions and ground deformation

Dangers of volcanoes

Lave flows,ash clouds,mass movement.

Magma

Molten rock beneath earth’s surface

Lava

Magma that has reached the surface

P waves 

Primary,fastest,travel through solids and liquids 

S waves 

Secondary,slower,travel only through solids 

Which waves cause more damage?

S waves cause more ground shaking

Ring of fire

A horseshoe-shaped zone around the Pacific ocean with frequent earthquakes and volcanic activity.

What are earthquakes

Sudden releases of energy due to fault movement

Where are earthquakes

plate boundaries,especially transform and convergent

What damage can earthquakes cause 

Ground shaking,surface rupture and tsunamis

Subduction definition

One tectonic plate sinks beneath another

Where is subduction located

Convergent boundaries

How are hot spots formed 

Plumes of hot mantle material rise and melt through the crust

What are the results of hot spots

Volcanic islands like chains of extinct volcanoes as plates move over the hot spot