lecture 16: earthscope and tsunamis no homework!€¦ · tsunami generation and hazards! 4. 4....

What we’ll learn today:!

1. 1. EarthScope Project (National Science Foundation)!2. 2. Seismic tomography and what it reveals about Earth’s

interior!3. 3. Tsunami generation and hazards!4. 4. Geologic ages!

Learning Objectives (LO)

Lecture 16: EarthScope and Tsunamis Read: Chapter 11 No Homework!

Seismic data confirm

the existence of discontinuities in Earth’s interior.

Discontinuities = changes in rock layers

• Earth Sciences version of Hubble Space Telescope!

• Named the #1 “Epic Project” by Popular Science in 2011!

• Thousands of scientists collaborating together = Big Science!

EarthScope: Enabling New Science!

Recording Earth’s Quakes

EarthScope Seismic Stations

EarthScope – National Science Foundation

US Array Records Passing of Seismic Waves

http://www.iris.edu/spud/gmv/4841

Seismic Tomography uses seismic data to make cross-sections of Earth’s interior

Seismic Tomography

cooler stuff warmer stuff

EarthScope is giving us images of Earth’s interior beneath the US

Combining Plate Tectonics with Tomographic Images

Cross-section of the mantle below the North American Plate

Inferred history of plate interaction between North American, Farallon

(old), and Pacific plates.

Seismic tomography reveals that Earth's interior :

a. Has four layers b. Has four layers interrupted by plumes c. Has discontinuities, with warm regions and cool

regions d. Has fast plates and slow plates e. Is made of olivine entirely to the inner core

iClicker Question

Banda Aceh, Sumatra, Indonesia

December 26, 2004 Magnitude 9.3

Tsunamis are NOT tidal waves

Underwater fault

1.

BIG earthquake

2.

Tsunami generated

3.

Tsunamis are seismic sea waves caused by earthquakes, landslides, eruptions of island

volcanoes.

Generation of a Tsunami

100 m

3 m

100 km

0.5 m

30+ m

1.5 to 3 km

airplane speed

Tsunami Wave Speeds

Travel Times (hours)

• 2004 Sumatra 350,000 deaths • 2011 Japan 15,000 deaths

Recent Destructive Tsunamis

Tsunami Example: Sumatra

http://www.youtube.com/watch?v=4yFNOuo_YxI

2011 Japan Tsunami

http://www.youtube.com/watch?v=9nTlgtf7TME

Disaster in the Pacific 3/11/2011

2011 Japan Tsunami

http://www.youtube.com/watch?v=w3AdFjklR50

Japan Earthquake: Helicopter aerial view video of giant tsunami waves

http://www.youtube.com/watch?v=5-zfCBCq-8I&feature=relmfu

Tsunami Wave Damage

Hawaiian Tsunamis?

Hilo, Hawaii 1960

Action Items for Thursday October 22

1. Read Chapter 11 2. No homework




GG101 Lecture 14: Geologic Time Geologic Time

GG101 Lecture 14: Geologic Time Time-history is preserved by rock layers Geology is the “Science of Time”

Geologic Time: 4.5 Billion years of Earth History

How was Geologic Time deciphered?

Example: In the mid-1600s, Archbishop James Ussher determined that the Earth was created on:

“nightfall preceding 23 October 4004 BC”

This date was included in some editions of the bible for hundreds of years.

Early estimates of Earth’s age were based on religion

Beginning in the 1700s, scientists used various methods to estimate Earth’s age

1860s: Lord Kelvin: 20 – 400 Million years, based on rock cooling rates (did not account for heat sources)

1780s: James Hutton: millions of years based on sedimentation rates “father” of geologic time “we find no vestige of a beginning, no prospect of an end”

1900s: Radiometric dating: 4.5 Billion Years

1800s: 100s of milllion yrs based on rates of: salt accumulation in ocean evolutionary change of fossils

Two components of Geologic Time 1. Relative Dating: Determine the order of geologic events 2. Absolute Dating: Assign ages to each different event

1. Deposition 2. Erosion 3. Intrusion 4. Faulting 5. Rock Deformation

Rock strata are formed by deposition of sediments in sedimentary environments

Relative Dating allows us to “order” five

fundamental geologic events

Rocks that are exposed to air or water are eroded. This erosion produces gaps in the geologic record called unconformitites.




An intrusion cuts across existing rocks




A fault cuts across existing rock. Faulting occurs in individual rocks and on the scale of the tectonic plates.




Deformation may tilt, fold, uplift and even invert existing rock layers. Deformation may expose rocks to erosion.




Relative dating of Grand Canyon rock layers

Can you determine the order of events that formed these layers?

To do this, geologists use

Seven Stratigraphic

Principles

Seven Stratigraphic Principles are used for Relative Dating

1. Principle of Superposition: Younger layers are deposited above older layers.

2. Principle of Original Horizontality: Layers are deposited horizontally.


3. Principle of Original Lateral Continuity: Sedimentary beds were deposited in unbroken layers.

4. Principle of Cross-Cutting Relationships: Geologic features that cut pre-existing rocks are younger that they cut.


5. Principle of Inclusions: A piece of rock that is incorporated into another rock layer is older that the rock layer.

6. Principle of Unconformities: An unconformity represents the passage of an unknown amount of time.


7. Principle of Fossil Succession: Fossils record changes to animals and plants that occurred through time (because of evolution)

Action Items for Thursday October 22

1. Read Chapter 11 2. No homework




lecture 16: earthscope and tsunamis no homework!€¦ · tsunami generation and hazards! 4. 4....

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