Transcript:

Hi my name's Shona from Geoscience Australia.

Today we're going to talk a little about how the earth works. I'm going to use this globe to help me. I'm just going to take this chunk out and have a look at the inside. There's lots of different layers to the globe, but we're going to focus on the outer layer; this one's called the crust. And you'll see that it sits underneath the ocean, and also it's thicker, and forms the land and the continents. And I want you to remember that the crust is made of rocks, but when you look outside, that's the top of the crust. Even if it's got vegetation and buildings on it, it's still the crust.

Now I'll pop this piece back, and I want you to now think of the globe -or the world- as a giant hard-boiled egg, with the thin shell representing the crust, and imagine that our shell is actually cracked up. It's broken into pieces. So, we're going to swap over now to looking at the world on a flat map, and it's been cut out into the shape of these pieces, that we call tectonic plates.

This is the first one we're going to have a look at; when you have a look at that shape, I suspect some of you will think it looks like a cat with one leg, or possibly a whale, or maybe even an alpaca. There's other things as well, you might have a wonderful imagination.

Now have I think about where this might be in the world. It might not be a shape that you recognize from looking at maps. It's actually our plate. We have Australia sitting here but the plate is much bigger. Continents are parts of plates, and our plate might include India as well, but some maps show them as separate, but remember, all that rock that's sitting there underneath the ocean -it's still part of our plate.

Now you might also know that tectonic plates move, and every plate moves in a different direction, at a different speed, while touching the neighboring plates around the edge.

So let's have a think about the direction that our plate moves, you might like to try to point either north, south west or east, have a go. I'll tell you, it's North, with a little bit of East, but we're mainly moving northwards. So, we're getting closer to the equator, and moving further away from Antarctica.

Now let's have a think about how fast we're moving. I'll put this down. Can you hold your fingers up to represent a distance that we move in one year? It could be anything from a millimeter all the way out to a meter - have a go.

Alright! The correct answer is about six or seven centimeters every year. Now some of you are going “Oh, that's not much!” but we are really fast compared to some other continents. Some of them doing less than two centimeters a year! In fact, Australia is currently the fastest moving continent in the world. That's a big deal.

Think about a lifetime for a human: one-hundred years of life. The ground will move seven meters in your life; that's a lot! Now I'm going to look at another plate, one of our neighbors -this is actually faster than Australia. So, I've said Australia's the fastest continent, this is the fastest plate. It's also the biggest! This is -well I call it Pac-Man plate- (you may or may not know what that means); it's actually the Pacific plate.

This is what's sitting underneath much of the Pacific Ocean, and it's moving to the west at 10 or 11 centimeters a year, and it's one of our neighbors. So, let me get this back, this is two plates together. Where plates are pushing into each other, you get lots of earthquakes happening, the rocks scrape past each other in some way, so around the edges of our plate, that's where most earthquakes happen.

You might be wondering, is Pac-Man eating Australia? No.

What happens is, the rocks underneath the ocean come along and then they slide underneath, but that's why we get lots of these earthquakes happening around New Zealand, and to the north. We get lots of earthquakes happening along this edge, as it slides underneath Indonesia up here.

So, what about Australia; do we get earthquakes? You might think no, they're all around the edges, but we do still get earthquakes. Not as big, not as many, but we do get them, because in some way or another our continent is getting stressed and every now and again those rocks will move.

Vocabulary bank:

Chunk - noun a substantial amount; a compact mass; verb group or chunk together in a certain order or place side by side; put together indiscriminately

layer - noun thin structure composed of a single thickness of cells; a hen that lays eggs; single thickness of usually some homogeneous substance; a relatively thin sheetlike expanse or region lying over or under another; an abstract place usually conceived as having depth; verb make or form a layer

crust - noun the trait of being rude and impertinent; inclined to take liberties; the outer layer of the Earth; a hard outer layer that covers something; verb form a crust or form into a crust

underneath - adv. under or below an object or a surface; at a lower place or level; directly beneath; on the lower or downward side; on the underside of

continent - adj. having control over urination and defecation; abstaining from sexual intercourse; noun the European mainland; one of the large landmasses of the earth

outside - adj. originating or belonging beyond some bounds:"the outside world"; on or toward an outer edge; leading to or from the outside; functioning outside the boundaries or precincts of an organized unit; very unlikely; relating to or being on or near the outer side or limit; (of a baseball pitch) on the far side of home plate from the batter; from or between other countries; coming from the outside; located, suited for, or taking place in the open air; adv. outside a building; on the outside; noun the outer side or surface of something; the region that is outside of something

top - adj. situated at the top or highest position; noun a garment (especially for women) that extends from the shoulders to the waist or hips; covering for a hole (especially a hole in the top of a container); a conical child's plaything tapering to a steel point on which it can be made to spin; platform surrounding the head of a lower mast; the greatest possible intensity; the highest or uppermost side of anything; the upper part of anything; the first half of an inning; while the visiting team is at bat; a canvas tent to house the audience at a circus performance; the top point of a mountain or hill; the highest level or degree attainable; the highest stage of development; verb finish up or conclude; cut the top off; strike (the top part of a ball in golf, baseball, or pool) giving it a forward spin; reach or ascend the top of; provide with a top; be at the top of or constitute the top or highest point; be the culminating event; pass by, over, or under without making contact; go beyond; be ahead of others; be the first

vegetation - noun inactivity that is passive and monotonous, comparable to the inactivity of plant life; an abnormal growth or excrescence (especially a warty excrescence on the valves of the heart); all the plant life in a particular region or period; the process of growth in plants

globe - noun a sphere on which a map (especially of the earth) is represented; the 3rd planet from the sun; the planet we live on; an object with a spherical shape

shell - noun the hard largely calcareous covering of a mollusc; ammunition consisting of a cylindrical metal casing containing an explosive charge and a projectile; fired from a large gun; the housing or outer covering of something; a very light narrow racing boat; a rigid covering that envelops an object; the exterior covering of a bird's egg; the hard usually fibrous outer layer of some fruits especially nuts; the material that forms the hard outer covering of many animals; hard outer covering or case of certain organisms such as arthropods and turtles; a metal sheathing of uniform thickness (such as the shield attached to an artillery piece to protect the gunners); verb remove from its shell or outer covering; look for and collect shells by the seashore; hit the pitches of hard and regularly; fall out of the pod or husk; remove the husks from; come out better in a competition, race, or conflict; use explosives on

imagine - verb form a mental image of something that is not present or that is not the case; expect, believe, or suppose

swap - noun an equal exchange; verb move (a piece of a program) into memory, in computer science; exchange or give (something) in exchange for

tectonic - adj. of or pertaining to construction or architecture; pertaining to the structure or movement of the earth's crust

suspect - adj. not as expected; noun someone who is under suspicion; a person or institution against whom an action is brought in a court of law; the person being sued or accused; verb imagine to be the case or true or probable; hold in suspicion; believe to be guilty; regard as untrustworthy; regard with suspicion; have no faith or confidence in

imagination - noun the formation of a mental image of something that is not perceived as real and is not present to the senses; the ability to form mental images of things or events; the ability to deal resourcefully with unusual problems

separate - adj. separated according to race, sex, class, or religion; independent; not united or joint; standing apart; not attached to or supported by anything; have the connection undone; having become separate; characteristic of or meant for a single person or thing; not living together as man and wife; noun a garment that can be purchased separately and worn in combinations with other garments; a separately printed article that originally appeared in a larger publication; verb divide into components or constituents; force, take, or pull apart; come apart; go one's own way; move apart; make a division or separation; discontinue an association or relation; go different ways; act as a barrier between; stand between; divide into two or more branches so as to form a fork; become separated into pieces or fragments; mark as different; arrange or order by classes or categories; separate into parts or portions; treat differently on the basis of sex or race

neighboring - adj. situated near one another; having a common boundary or edge; touching

direction - noun a general course along which something has a tendency to develop; a message describing how something is to be done; a line leading to a place or point; the spatial relation between something and the course along which it points or moves; the act of setting and holding a course; the act of managing something; the concentration of attention or energy on something; something that provides direction or advice as to a decision or course of action; a formal statement of a command or injunction to do something

equator - noun an imaginary line around the Earth forming the great circle that is equidistant from the north and south poles; a circle dividing a sphere or other surface into two usually equal and symmetrical parts

millimeter - noun a metric unit of length equal to one thousandth of a meter

meter - noun any of various measuring instruments for measuring a quantity; rhythm as given by division into parts of equal duration; (prosody) the accent in a metrical foot of verse; the basic unit of length adopted under the Systeme International d'Unites (approximately 1.094 yards); verb measure with a meter; stamp with a meter indicating the postage

compare - noun qualities that are comparable; verb examine and note the similarities or differences of; consider or describe as similar, equal, or analogous; to form the comparative or superlative form on an adjective or adverb; be comparable

lifetime - noun the period during which something is functional (as between birth and death)

earthquake - noun shaking and vibration at the surface of the earth resulting from underground movement along a fault plane of from volcanic activity; a disturbance that is extremely disruptive

slide - noun the act of moving smoothly along a surface while remaining in contact with it; a transparency mounted in a frame; viewed with a slide projector; a small flat rectangular piece of glass on which specimens can be mounted for microscopic study; plaything consisting of a sloping chute down which children can slide; (geology) the descent of a large mass of earth or rocks or snow etc.; sloping channel through which things can descend; (music) rapid sliding up or down the musical scale; verb move smoothly along a surface; move obliquely or sideways, usually in an uncontrolled manner; to pass or move unobtrusively or smoothly

edge - noun a sharp side formed by the intersection of two surfaces of an object; a strip near the boundary of an object; a slight competitive advantage; the attribute of urgency; the boundary of a surface; a line determining the limits of an area; verb provide with an edge; advance slowly, as if by inches; lie adjacent to another or share a boundary; provide with a border or edge

stress - noun the relative prominence of a syllable or musical note (especially with regard to stress or pitch); (physics) force that produces strain on a physical body; difficulty that causes worry or emotional tension; special emphasis attached to something; (psychology) a state of mental or emotional strain or suspense; verb put stress on; utter with an accent; to stress, single out as important; test the limits of