Plates on the Move

Geology Rocks! Plates on the Move 6ES Science Std: 1c Chapter 6 – Section 3

We have identified the tectonic plates The Lithosphere is broken up (divided) into parts Each of these parts of the lithosphere is called a plate

And these plates are moving…. The red arrows show motion direction But how do we know that they are moving?

How to tell if something is moving…… Car map systems can tell…… But how do they know that they are moving?

They use satellites Global Positioning System or GPS GPS uses satellites and receivers to find out exact positions Each GPS satellite transmits data that indicates its location and the current time There are at least 24 operational GPS satellites at all times

So how does GPS work? Each GPS receiver also has a clock that is synchronized with the time on the satellites Each GPS satellite has a very accurate clock

So how does GPS work? All satellites transmit data to the receivers at the same time • The signals, moving at the speed of light, arrive at a GPS receiver at slightly different times because some satellites are farther away than others.

So how does GPS work? • A GPS receiver "knows" the location of the satellites, because that information is included in satellite transmissions • By estimating how far away a satellite is, the receiver also "knows" it is located somewhere on the surface of an imaginary sphere centered at the satellite

So how does GPS work? • It then determines the sizes of several spheres, one for each satellite.

So how does GPS work? • Most hand-held GPS units have about 10-20 meter accuracy You are here

So how does GPS work? • You need at least 3 satellites to tell you where you are on the surface of the Earth…. You are here • You need 4 to tell altitude or elevation

So now that you know where you are…. You can use GPS to tell how fast you are going The change in position over time…. Tells the receiver direction and speed it is moving

So now that you know where you are…. You can use GPS to tell how fast you are going Instead of the car moving….. Geologists put a spike in the ground and see how far it has moved… Because the ground is moving It seems like the spike is moving And you can see how fast the ground is moving

If you look at all the places that are monitored On this map, the arrows tell a lot of information

If you look at all the places that are monitored The way the arrow points is the direction moved

If you look at all the places that are monitored The longer the arrow – the faster the movement

We have 3 “Spikes” close to here… We are here… All Three are this direction

We have 3 “Spikes” close to here…

We have 3 “Spikes” close to here… Corner of Devonshire and Louise Avenues Buried beneath the street is a steel disk DELO Monitoring Station

We have 3 “Spikes” close to here… CSN1 Monitoring Station On the CSUN Campus Near the corner of Fullerfarm and Zelzah

We have 3 “Spikes” close to here… Near the corner of Nordhoff and Tampa Between the Best Buy and the Bed, Bath and Beyond Near metro railroad tracks NRID Monitoring Station

We have 3 “Spikes” close to here… Over time movement is measured The speed and direction is recorded It shows that Granada Hills is moving We are moving at a speed of….. Around 38 mm per year in a NW direction (Towards San Francisco)

We have 3 “Spikes” close to here… That means……. NOVA is moving 3.78 cm per year Question: How far has NOVA moved in the time you have been alive? Distance traveled = 3.78 cm/year x your age If you are 12 we have moved around 45.4 cm

We have 3 “Spikes” close to here… Here is the CSN1 Data….. Avg27.70 mm/yr In 8 years we have moved 221.6 mm North and 205.6 mm west Avg25.70 mm/yr We have also gone down 8.8 mm in elevation Avg-1.10 mm/yr

We have 3 “Spikes” close to here… Food for Thought….. If NOVA is moving 3.78 cm per year… How far would it move in 100 years? Is this a big distance or a small distance?

It has been measured….. …that the Mid Atlantic Ridge has been making new crust at a rate of 4 cm/year If the coast of South America is about 676 million cm from the Coast of Africa Distance = Speed x Time Or Time = Distance / Speed Answer: 169 million years ago How long ago were they joined together? Question: When did the dinosaurs go extinct?

Quick check…… How does a GPS receiver determine its location? What data is transmitted by GPS satellites? How accurate is GPS? 4. How many satellites do I need to get an accurate position on the surface of the Earth? Work in pairs to answer these questions on separate sheets of paper

Questions?

Plates on the Move