Plate tectonics

what are the layers of the earth

• Crust } Together these are called the

• Astheosphere } lithosphere

• mantle

• outer core

• inner core

what are the qualitys of the asthenosphere

• Plasticy

• Liquid and solid

• moves tectonic plates allowing lisosphere to float and move

what are the four types of boundry

• Destructive

• Consructive

• Conservitive

• Collison

what is this plate boundry and how does it form

Destructive/Convergent

• Plates move towards each other

• the denser plate subducts

• subducted plate melts into the mantle

• magma rises through the cracks forming a magma chanmber

what landforms form at a destructive plate boundry and examples

• Fold mountins

• Ocean trenches

• Composite volcanos

Eg. Andes mountins on the Nazaca + south american plate

what boundry is thios and how does it occour

Conservitive

• Plates move parre;el to each other

• in diffrent directions, angles or speeds

• pressure builds

• a sudden release causes earquakes

• no crust is created or destroyed

what forms at an conservative plate boundry and examples

• Fault lines

• linear valleys

Eg. Sans Andreas fault, paciffic plate + North american plate

what plate boundry is this and how does it form

Constructive/divergent

• Convection currents cause magma to rise and fall

• rising magma pushes the plates apart

• pressure is reduced leading to decomposition melting

• magma rises through the gap

• magma cools creating new crust

what forms at a constructive plate boundry and examples

• Mid-ocean ridges

• rift valleys

• shield volcanos

Eg. Mid atlantic ridge on the North American + Eurasian plates

what plate boundary is this and how does it form

Collison plate boundry - Type of destructive plate boundry

• two continental plates move towards each other

• both are the same density

• the crust compresses and buckles

• rock layers fold

• large mountin ranges form

what forms at collison plate boundrys with examples

• Fold mountins

• High plathues

Eg. Hymilayas on the indian and eurasian plate

what are the two waves that support evidence for the earths structure

• P-waves - solid and liquidW

• S-waves - only travel through solid

What landforms form on destructive plate boundrys

• Island Arcs

• Fold mountains

• Composite volcanos

• Ocean trenches

What landforms form on contructive plate boundrys

• shield volcanos

• oceanic ridges

what land form is this and how does it form

Island Arc

A long curved chain of volcanic islands formed at a destructive plate boundry where two oceanic plates meet

1. two oceanic plates converge the denser plate subducts

2. ocean water is drawn into the mantle reducing melting point and forming magma

3. magma travels through the crust and rises to the surface

4. due to the earth bieng spherical it creates an arc

what landform is this and how does it form

Fold mountins

piles of cotinental crust sitting uppon the lithosphere forced upwards on the surface of the earth

1. plates converge at the same density

2. pressure builds and forces the plates upwards

3. continental crust piles up ontop of the lithosphere

what landform is this and how does it form

Composite volcanos

steep sided, cone shaped volcaanos built from alternating layers of thick ash and lava forming a conical shape

1. subduction occours

2. intense heat and pressure means crust is melted making magma

3. magma has a high viscosity amd it rises to form a chamber

4. presure builds due to gas and makes an explosive reaction with pyroclasic flow

5. prosess repeats and is explosive

what is this landform and how is it made

Shield volcano

Gently sloping sides wide volcano formed by low viscosity lava that spreads out over long distances, broad and shallow sides

1. magma is balstic with a low silica content and viscosity

2. when erupted lava is very fluid and traves far and quickly

3. each eruption spreads a thin layer over a wide area which builds up

Constructuve and hot spot plate boundrys

what landform is this and how does it form

Ocean ridges

Long continuous underwater mountin chains as plates move apart and magma rises through the gap to create new volcanic crust

1. Plates move apart due two to covection currents

2. gap is formed and magma rises through the gap due to a decreace in pressure

3. new crust forms as magma cools and solidifys forming an underwater mountin chain

what landform is this and how does it form

ocean trench

long, narrow depressions in the ocean floors made where one tectonic plate had subducted under another

1. two plates mover towards each other

2. deser plate subducts

3. creates an deep depresion in the ocean floor

4. this continues

5. pressure and friction cause earthquakes and volcanic activity

give an example of an ocean trench

Mariana trench

• Western paciffic ocean

• pacific plate subducted beneath

give an example of an ocean ridge

Mid-atlantic ridge

• Eurasion and north american plate

give an example of a sheild volcano

Mauna Loa

• Hawaii

• Covers 5% of the island

• paciffic plate over hawian hot spot

Give an example of an island arc

Aleitian islands

• North american plate and pacific

give an example of an fold mountain

Himalayas

• southern Asia

• Indian plate and Eurasian plate

give an example of a composite volcano

Mount st. Helens

• Juan de fuca plate and North american plate

what is subduction

The process by which a dense oceanic plate is forced beneath a less dense continental plate (or another oceanic plate) at a convergent plate boundary.

what is sea floor spreading

The process by which new oceanic crust is created at mid-ocean ridges (divergent plate boundaries). Magma rises from the mantle through the ridge, solidifies, and pushes the existing crust outward in both directions.

what are convection currents

The mechanism within the semi-molten asthenosphere. Heating and cooling causes the movement of matirial and currents drag overlying tectonic plates

what are hot spots

Fixed points of intense volcanic activity within the mantle, independent of plate boundaries. A mantle plume of exceptionally hot material rises through the mantle and burns through the overlying plate, creating a volcano at the surface.

what is sea floor spreading

symmetrical bands of alternating magnetic polarity either side of mid-ocean ridges confirm new crust is created at ridges and plates spread outward

charecteristics of the oceanic crust

• denser

• basaltic composition,

• thinner

• subducts at convergent boundaries.

charecteristics of continental crust

• less dense

• granitic composition

• thicker

• Cannot subduct

• it buckles upward at collision boundaries.

what are hot spots

• Fixed points of intense volcanic activity within the mantle, independent of plate boundaries

How do hot spots cause island chains

• A mantle plume of exceptionally hot material rises and burns through the overlying plate, creating a volcano at the surface

• As the plate moves over the fixed hot spot, a chain of progressively older volcanic islands forms

• Example: Hawaiian island chain and Mauna Loa shield volcano

Can I have an example of floor spreading ocianic rate

Mid-Atlantic Ridge spreading rate: ~2.5 cm/yr

example of constructive continental landform rate

East African Rift Valley

Example of the rate at a collision boundry

Himalayas still rising at ~5 mm/yr

how deep is the arriana trench

11 km