Plate Boundaries. Remember: Earth Structures Lithosphere Asthenosphere

Plate Boundaries

Remember: Earth Structures

LithosphereAsthenosphere

Plate Tectonics

1. Plates are moving in different directions at different speeds.

2. Movement caused by convection in asthenosphere.

Plate boundary = place where two plates meet.

Plates and BoundariesTwo types of crust:1. Oceanic crust2. Continental crust

Three types of boundaries:1. Collide2. Separate3. Slide past

Fault – Border of plate boundaries

Convergent Boundary

Plates collide3 types based on types of crust

colliding1. Continental-continental

◦Create mountains◦Examples

Warm-up

Put Impact List in red box

Which piece of evidence for plate tectonics do you think is most compelling and why? Compelling: strong and forceful, having

influence

You find an axe made of stone containing Uranium-235. You determine it has undergone 7 half lives. What percentage of U-235 is remaining and how old is the axe? (Half life of U-235 is 703.8 years)

Convergent Boundary2. Oceanic-oceanic

◦Older plate is subducted (more dense)◦Subduction forms trench◦Example

3. Continental-oceanic◦Oceanic is subducted◦Creates: Trenches Volcanoes

◦Example

Warm-up

What are the three different convergent boundaries? What does each one cause?

Based on the movements of the other types of boundaries (look back in your notes!) – what do you predict they cause?

Divergent BoundaryPlates separate

◦Space fills with magma◦Creates new crust◦Pushes old out

2 types

Divergent Boundary

1. Continental-Continental or on Continental Plate

◦ Creates rift valley May become lake Examples

Iceland

Divergent Boundary

2. Oceanic-Oceanic◦ Spreading center◦ Mid-ocean ridge◦ Majority of Earth’s volcanoes

Non-explosive

Transform BoundaryPlates slide past each other Not a smooth movementNo creation or destruction of crust

Earthquakes!

San Andres Fault

Hand-Signals…Show me:

1. Convergent boundaries = Collide

2. Divergent boundaries = Dividing

Check for understanding

What type of boundary is this?

Check for understandingIs the following picture:1. Convergent boundaries2. Divergent boundaries

Check for understandingIs the following picture:1. Convergent boundary2. Divergent boundary

Volcanoes!

Explosive EruptionsRare

◦Total number: DestructiveProduce

◦Debris◦Ash◦Gas

Pyroclastic Flow

Pyroclastic FlowsLarge amount of

material produced in small amounts of time

Temperatures greater than 700 deg. Celsius

Faster than a hurricane

Lahar

Deadly

Non-explosive Eruptions Most common

Produce◦Huge amounts of

lava◦Calm lava flows

Shape our world◦Islands in the

Pacific◦Sea floor

Create a modelCreate a model to help you learn

the different types of plate boundaries.

You will be adding one more type tomorrow.

Be sure to include each subtype of each of the two boundary types we talked about today.

Warm-up 11/101. How are convergent and divergent

boundaries similar? 2. Give a current example of a

convergent boundary and what is being formed there.

3. What type of plate boundary is seen here How do you know?

Hot Spots

PhenomenonTheories

◦Mantle plumes◦Cracks in crust

Far from boundary◦Examples

Appear to move over time

◦Why?

Warm-up 11/11-12What type of boundary creates mountains? Be specific.

Radiometric dating is _________ dating.Which layer of the Earth is responsible for the movement of tectonic plates?

The half-life of plutonium is 6530 years. A sample contains .39% of the original amount of plutonium. How many half-lifes have passed and how old it it?

EarthquakesWhat are they? What is it like?SeismologistWhere?

◦Plate boundary◦Occur at faults◦Varying depths◦Focus

Epicenter

How are earthquakes measured?

Richter scale◦ Strength

(magnitude)◦ Measuring ground

motion◦ Used by the media

Moment magnitude◦ More precise◦ Measures the

energy released◦ Measured at the

epicenter◦ Used by scientists

Largest Recorded Earthquakes

Recent earthquakes Tracker

Imaging of Earthquake Waves

Seismograph◦Measures and records local movement

◦3 main waves1. P wave2. S wave3. Surface

waves

Earthquake Waves

P waves◦ Primary◦ Fastest - First detected◦ Back-and-forth

S waves◦ Secondary◦ Side-to-side◦ Slower, arrive later

Surface◦Last to arrive◦Rolling◦Side-to-side◦Close to surface◦Slowest◦More destructive

Aftershocks

Foreshocks

Finding the EpicenterDistance vs. time

graph is constant◦Closest has

smallest time difference

Measure time difference on local seismograph◦Compare to graph◦Find distance

Repeat for multiple locations

Finding Epicenter continued…

Use distances found

Draw a circle from each site

Overlap = epicenter

Need at least 3 points

Warm-up1. Which type of plate boundary do you think has the greatest impact on society? Justify your answer.

2. If the P wave of an earthquake arrives at 10:45 am and the S wave arrives at 10:55 am, how far are you from the epicenter?

Earthquake Hazard Map

Earthquake PredictionNot exactSeismic gaps

◦Area of fewer earthquakes

◦Likely location of future earthquake

◦Used to predict 1989 San Francisco

Past frequency

Destruction from EarthquakesLiquefaction

◦ Mixing soil with underground water

◦ Sinkholes LandslidesFire

◦ Broken gas and electrical lines

◦ Lack water to fight

Building and highway damage

Hand-Signals…Show me:

1. Convergent boundaries = Collide

2. Divergent boundaries = Dividing

3. Transform boundaries = Slide

What type of boundary is this?

TsunamiHow?

◦Displacement of a large volume of water

◦CausesMassive waves

◦Wavelength◦Height◦Period

Impacts coastline◦Wave slows◦Increases in

height

Tsunami warning system

Only a few a yearMost recent (major)

◦Indonesia (Dec. 2004)

◦Japan (Mar. 2011)Seiche

Ring of Fire

To learn more about the dinosaur, I would find and observe the layers that the fossil was found in. This would help to find the relative age the fossil is and could find out the order of the geological events that happened in the layer like a fault or intrusion. With the little bones they found, they can use carbon-dating to find the absolute age and what time period it was in. Using its age, they could find out where the dinosaur lived because the continents used to be in different places during a certain time period, if the dinosaur was in that time period they could examine its jaw and teeth structure to find what it would eat. If they find what it eats, they could help determine where it lived; for example, if it ate plants they could narrow the location to where the climate could sustain plants. If it ate meat, they could find animals that lived in the same time period and animals that are prey to the size of this dinosaur and find other animals’ locations to narrow where this dinosaur lived. To find out more about this dinosaur they could use carbon-14

that was in the body to tell how old it is. They could look in the same rock layer that is was found to tell the climate of the area around the dinosaur. They may find fossils of plants or other animals near that area, then check its mouth for what type of teeth it has, that’s why the other fossils are needed so they could know what it ate – if it was an herbivore, carnivore, or omnivore.