Science Year 9 Semester 2-Plate Tectonic Theory Test Study

Convergent plate boundary:

-2 plates collide -Rock is destroyed here so they are also called destructive plate boundaries -These form a range of land features: Mountains,Chains of islands,Underwater trenches

Continental Drift:

-Continental Drift is the movement of the continents from a huge land mass called Pangea.

Continental Crust:

-Crust forming the continents -Above sea level -Thicker,contains Granite -Less dense (due to containing lighter elements such as aluminium and silicon)

What are Earthquakes?

-Earthquakes are the rapid movement of the ground back and forth or up and down in a wave motion -Due to friction between tectonic plates -Nearly all earthquakes start at the edges of the tectonic plates -Most of the strongest earthquakes occur near converging plate boundaries

Anticlines:

-When the folds bend up in the middle = ANTICLINES

Folds

-occurs when forces in the Earth are large enough to cause layers of rock to bend and crumple without breaking. -example=

Describe how the discovery of fossils led us to decide that there must have been a supercontinent called Pangea?

-Evidence for Pangea includes fossil distribution, distinctive patterns in rock strata in now unconnected parts of the world and the distribution of the world's coal. -In terms of fossil distribution, archaeologists have found matching fossil remains if ancient species in continents are separated by thousands of miles of ocean today.

The Crust Layer:

-Is the outer layer of the earth. It is a thin layer between 0-60 km thick. The crust is the solid rock layer upon which we live.

What earthquakes are measured in?

-Measured using an instrument called a seismometer -Most modern day seismometers are electronic -The trace of a seismometer is called a seismograph -Record the size and duration of the earthquake

2nd Fault: Reverse Fault

-One chunk of crust moves upwards along a fault line.

1st Fault:Normal Fault

-One chunk of crust slips vertically down the crack or fault line

3rd Fault:Strike-Slip Fault

-The crusts move horizontally past each other. -E.g. The San Andreas fault.

Explain how it causes crustal movement:

-The force that causes most of the plate movement is thermal convection, where heat from the Earth's interior causes currents of hot rising magma

The Inner Core Layer:

-The inner core is in the centre and is the hottest part of the Earth. -With its immense heat energy, the inner core is like the engine room of the Earth. -iron and nickel with temperatures of up to 5,500°C. With its immense heat energy,

The Outer Core Layer :

-The outer core is the layer surrounding the inner core. -It is a liquid layer, also made up of iron and nickel. -It is still extremely hot, with temperatures similar to the inner core.

Some of the main tectonic plates on Earth:

-The outer shell of the earth, the lithosphere, is broken up into tectonic plates. -The seven major plates are the African plate, Antarctic plate, Eurasian plate, Indo-Australian plate, North American plate, Pacific plate and South American plate.

What is the 'Ring of Fire'

-The ring of fire is a major area in the basin of the Pacific Ocean where a large number of earthquakes and volcanic eruptions occur.

The Mantle Later:

-The widest section of the Earth. It has a thickness of approximately 2,900 km. -The mantle is made up of semi-molten rock called magma. -In the upper parts of the mantle the rock is hard, but lower down the rock is soft and beginning to melt.

Synclines:

-When they bend down in the middle = SYNCLINES

Divergent plate boundary:

-mainly occur in oceanic ridges but can occur on land -example is this divergent fault in Iceland -The same thing happens: magma rises up and forms new crust at the surface

Define 'convection current'

Convection is one of the three main types of heat transfer, the other two being conduction and radiation.

Oceanic Crust:

Found on ocean floor -Below sea level -Much thinner,contains Basalt -Much denser (due to containing heavier elements such as iron and magnesium)

Structure Of The Earth Sections:

Four concentric layers: inner core, outer core, mantle and crust. The crust is made up of tectonic plates, which are in constant motion. Earthquakes and volcanoes are most likely to occur at plate boundaries.

Explain what a 'hot spot' is:

Hotspots were thought to be caused by a narrow stream of hot mantle convecting up from the mantle-core boundary called a mantle plume

Faults

Occurs when forces acting on rocks become very large causing them to crack and move -There are 3 different types of faults:

Subduction:

Occurs when oceanic plate collides with a continental plate

Plate Tectonics:

Plate tectonics is the theory that Earth's outer shell is divided into several plates that glide over the mantle, the rocky inner layer above the core.

Theory Of Plate Tectonics:

Plate tectonics means "plate structure" -Developed in the 1960's as a theory to explain the movement of the Earth's plates. -The plates are moving 1 to 10 cm per year. -Most of the Earth's seismic activity (volcanoes and earthquakes) occurs at the plate boundaries

Focus:

The location where the earthquake begins. The ground ruptures at this spot, then seismic waves radiate outward in all directions.

Epicentre:

The point on the Earth's surface located directly above the focus of an earthquake.

How each level is measured mathematically?

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