Tectonics and Geology

Tectonics and Geology

Plate tectonics review

Transform boundary

Where two plates move past each other

Commonly cause earth quakes. San Andreas fault in California is a good example.

Divergent boundary

• Where two plates move apart

• Forms a ridge that fills with water, this is how the oceans formed after Pangaea

• Makes the youngest crust, this is why ocean crust is the youngest crust

Convergent - continental oceanic

• When two plates collide together.

• The more dense oceanic plate will slide under (subduct) the more buoyant continental plate.

• Often causes tsunamis, earth quakes, and volcano eruptions. Ring of fire is most prominent example.

• Cause mountains to form off coast think Appalachian, and pacific rim.

Convergent - continental continental

• When two continental plates collide neither subducts

• Instead they both go up to form mountains.

• Himalayas are an example of this.

Plate movement

• Plates move on the convection currents of the mantle

• Currents are caused as hot magma moves up and cold magma moves down

• Plate movement is accelerated by the weight of subducting portions of the plate pulling the rest in.

Multiple Choice

What do you call the boundary of two plates moving apart from each other?

• Divergent

• Convergent

• Transform

• separating

Multiple Choice

What do you call the boundary of two colliding plates?

• Divergent

• Convergent

• Transform

• Collision

Multiple Choice

What do you call the boundary of two plates moving past each other?

• Divergent

• Convergent

• Transform

• Collision

Multiple Choice

When oceanic and continental plates converge which one sub-ducts

• Oceanic

• Continental

• Both

• Niether

Multiple Choice

What causes the movement of the plates?

• Gravity

• Magic

• Convection currents in the mantle (asthenosphere)

• Convection currents in earth's atmosphere (lithosphere)

Multiple Select

At what boundaries are most likely to have earthquakes? (choose 2)

• divergent

• transform

• convergent

Earths geological clock

Objectives

• Understand concept of uniformatism

• understand superposition

• Difference between relative and absolute dating

• How superposition helps dating rocks and fossils

The Grand canyon has been formed by the Colorado river cutting through the rocks. Each different layer of rock represents a different era in which it was formed. You can find the same rock in other locations as well.

Can you think of other places where you've seen layers of rock?

Strata are layers of rock those further down are older than those found near the surface. This is the basis for the law of superposition.

Open Ended

How does the law of superposition help us to date fossils and rocks?

Strata can be disturbed by tectonic movements to cause bends (shown in picture), breaks, or tilts

Magma will sometimes force its way through the rock layers. These are called intrusions. Intrusions will always be younger than the rocks it's intruding through.

Open Ended

Why will intrusions be the youngest rocks in the formation?

Multiple Choice

Order the layers from oldest to youngest

• A, B, C, D

• C, B, D, A

• C, B, A, D

• C, E, B, D, A

Open Ended

At what point in time did the break take place? Name the layer that it happened before or after.

- Knowing the exact age of an object, i.e. 10.000 years old is called absolute age

- Knowing the relative age of something i.e. between 10-20 million years old, is called relative age.

- Remember that fossils will always be older than the rock layer they are found in.

Absolute age methods

• Carbon 14 dating

• Counting tree rings

• radioactive decay of isotopes

• paleomagnetism

• Used to measure things that are thousands to tens of thousands years old

Let's apply

What happened to the dinosaurs?

Open Ended

What do you already know about what happened to the dinosaurs? What evidence do you know to support that theory?

Prevailing theory

Scientists generally believe that dinosaurs went extinct after a meteor collided with earth. Using the fossil record and the theory of uniformitarianism we can recreate what caused the extinction.

Fossil and geological evidence

• Fossils of dinosaurs and the plants they lived with are 66 million years or older

• Thin strata of rock called K-Pg boundary that contains high levels of Iridium, a rare earth metal commonly found in meteorites, and pieces of tektite, type of glass formed from debris falling back to earth through the atmosphere.

Uniformitarianism

• Uniformitarianism is the idea that processes and natural laws at work in the present functioned the same in the past.

Finding other examples

We can use crater impacts on the moon to study what we think happened on earth 66 million years ago. Notice that there are two circles formed from the impact, an outer and inner ring.

Finding the crater on earth

Scientist were able to find a similar two ring pattern using a satellite mapping technique called gravity mapping. Based on what was studied on the moon scientist estimate that the meteorite was 10-15 km (6-9 mi.) in diameter. Mount Everest is just under 9 km high for comparison.

So what happened?

• Fire storms - for a few hours after the impact debris falling back to earth raised the temperature on earth cooking anything exposed

• Most of those that survived the firestorm died from Ecological collapse - sun was blotted out for a year cooling temperatures, disrupting photosynthesis, acid rain became a constant, and the ocean acidified significantly.

Open Ended

What pieces of evidence are we leaving of our passage? Were we to go extinct what would they be able to tell about us from the fossil record?

A new epoch?

• Major climate changes can be seen in the fossil record and strata

• Major climate change is the reason for most extinction events

• Some are suggesting that the climate is changing enough that we're leaving the Holocene era entering a new epoch they're calling the anthropocene

Let's review

Multiple Choice

Which statement is true about the layering of earths crust?

• Younger rocks are found deeper

• Older rocks are found deeper

• No way to tell

Multiple Choice

Why are marine fossils found in and on mountains?

• Animals that make shells migrate

• It's a common practice for humans to carry sea shells to mountains

• As sea beds dry out they can be uplifted or relocated by geologic activity

Multiple Choice

The law of superposition can help determine what?

• The absolute age of strata

• The relative age of strata

• Which strata is 66 million years old

Multiple Choice

Which technieque is useful for dating fossils that are millions of years old

• C14 dating

• uranium isotope dating

• superposition

• paleomagnetism

Multiple Choice

How does the K-Pg layer support the asteroid theory for mass extinction?

• It's only found in Mexico where the meteor impacted.

• This thin band contains the youngest dinosaur fossils we have found.

• The thin band contains metals at concentrations not found in earths crust.

• It doesn't scientist just make stuff up so we'll keep paying them.

Multiple Choice

Why do scientist believe we've started a new epoch?

• trick question, they don't believe we have

• Humans have adapted the environment so much that it's changing the eco system if the entire planet

• Every few million years the earth goes through a natural climate changing process that signals a new epoch

• They've been able to identify a new strata associated with our current epoch.