““How Did Those Rocks Get Up There? How Did Those Rocks Get Up There? Exploring Lake Smerdyachee, Russia”Exploring Lake Smerdyachee, Russia”

Earth2Class Workshops for TeachersEarth2Class Workshops for TeachersLamont-Doherty Earth ObservatoryLamont-Doherty Earth ObservatoryOriginally presented 18 April 2015Originally presented 18 April 2015

Presented byPresented by

Dr. Dallas AbbottDr. Dallas Abbott

LDEO Research Scientist LDEO Research Scientist

dallas@ldeo.columbia.edu

Dallas has shared her research and data about impacts of asteroids, meteorites, and other extraterrestrial objects with us since 2002. Her studies have taken her to many parts of the world, from Australia and New Zealand to the Hudson River and the continental shelf off NJ/NY.

Today, she’ll discuss ongoing work in an area about 140 km east of Moscow, Lake Smerdyachee.

Some important concepts about impact cratersSome important concepts about impact craters

Form when a bollide (meteorite, asteroid Form when a bollide (meteorite, asteroid or comet) collides with a solid object or comet) collides with a solid object (planet or moon)(planet or moon)

Easily seen on our Moon, Mercury, and Easily seen on our Moon, Mercury, and Mars, where weathering and erosion are Mars, where weathering and erosion are slow slow

Often hard to recognize on Earth because Often hard to recognize on Earth because of the effects of weathering and erosionof the effects of weathering and erosion

Meteor Crater (Barringer Crater) in Meteor Crater (Barringer Crater) in Arizona was among the first recognizedArizona was among the first recognized

http://cass.jsc.nasa.gov/images/scraters/scraters_S10.gif

Impact craters on land have been known and studied for many years. This STS-9 image of Manicouagan Crater in northern Canada shows the remains of a collision estimated to have taken place 215 million years ago. It’s about 85 km in diameter.

http://antwrp.gsfc.nasa.gov/apod/ap001213.html

Many other craters have subsequently been Many other craters have subsequently been identified, especially by remote sensingidentified, especially by remote sensing

Approximately 190 are confirmed, with Approximately 190 are confirmed, with many other suspectedmany other suspected

Mostly within the stable cratons of North Mostly within the stable cratons of North America, Africa, Australia, and EuropeAmerica, Africa, Australia, and Europe

Earth’s greater gravitation pull probably Earth’s greater gravitation pull probably means it has been hit more, but water, means it has been hit more, but water, atmospheric weathering, and plate atmospheric weathering, and plate tectonics have destroyed or hidden many tectonics have destroyed or hidden many impact sitesimpact sites

High velocities at which meteoroids collide High velocities at which meteoroids collide with Earth explain the great effects from with Earth explain the great effects from

even small objectseven small objects

Velocities range between 11.2 km/sec Velocities range between 11.2 km/sec (escape velocity from Earth) and 72 km/sec (escape velocity from Earth) and 72 km/sec (orbital velocity of Earth plus escape (orbital velocity of Earth plus escape velocity of solar system)velocity of solar system)

Kinetic Energy released is proportional to Kinetic Energy released is proportional to square of velocitysquare of velocity

Effects is that meteorites are, gram for Effects is that meteorites are, gram for gram, more than 100x as powerful as TNT!gram, more than 100x as powerful as TNT!

Methods to identify impact locations Methods to identify impact locations include:include:

Siderophile elements (esp. Ir, Os, and Pt) Siderophile elements (esp. Ir, Os, and Pt) in “impact melt rocks”in “impact melt rocks”

““Shock metamorphism” in “target rocks” Shock metamorphism” in “target rocks” and mineralsand minerals

““Shatter cones”Shatter cones”High-pressure mineral phases, such as High-pressure mineral phases, such as

stishovitestishovite ““Diaplectic glass” and tektites in “ejecta Diaplectic glass” and tektites in “ejecta

blankets”blankets”

Many craters or remnants have been Many craters or remnants have been recognized by the presence of rare elementsrecognized by the presence of rare elements

““Siderophile elements” such as Ir indicate Siderophile elements” such as Ir indicate that terrestrial clays have been mixed with that terrestrial clays have been mixed with extraterrestrial materialsextraterrestrial materials

One of the best studied is the subsurface One of the best studied is the subsurface Chicxulub structure in Mexico, widely Chicxulub structure in Mexico, widely accepted at the location of the Cretaceous-accepted at the location of the Cretaceous-Tertiary boundary eventTertiary boundary event

Not exposed at the surface, it has been identified through geophysical studies of the gravitational field. Located near 21°N 90°W, the structure has a diameter of ~250-280 km. Its age has been calculated at 64.98 ± 0.05 million years

http://cass.jsc.nasa.gov/images/scraters/scraters_S37.gif

Impact Craters are classified as Impact Craters are classified as “Simple” or “Complex”“Simple” or “Complex”

““Simple Craters” are relatively small, have Simple Craters” are relatively small, have a smooth bowl shape, and a a smooth bowl shape, and a depth:diameter ratio of 1:5 to 1:7depth:diameter ratio of 1:5 to 1:7

““Complex Craters” are largely and show Complex Craters” are largely and show the effect of gravitational collapse of the the effect of gravitational collapse of the walls to produce a central peak or peak walls to produce a central peak or peak ringring

Connections between impacts and Connections between impacts and mass extinctions provide evidence for mass extinctions provide evidence for the still-unproved theory that such the still-unproved theory that such events may be the “metronome that events may be the “metronome that sets the cadence for biological sets the cadence for biological evolution on Earth.” evolution on Earth.” (Koeberl and Sharpton)(Koeberl and Sharpton)

What might happen when an impact occurs What might happen when an impact occurs in the ocean? Tsunami!in the ocean? Tsunami!

A tsunami is a giant sea wave or series of waves A tsunami is a giant sea wave or series of waves caused by disruption of the ocean surfacecaused by disruption of the ocean surface

Most tsunamis are connected with earthquakes Most tsunamis are connected with earthquakes or volcanic eruptions, but some may be caused or volcanic eruptions, but some may be caused by meteorite or asteroid collisionsby meteorite or asteroid collisions

For more information about tsunamis, go to For more information about tsunamis, go to http://www.geophys.washington.edu/tsunami/welhttp://www.geophys.washington.edu/tsunami/welcome.html come.html

Where Are Impact Craters Found?Where Are Impact Craters Found?

The “Fount of All Wisdom” (Wikipedia) The “Fount of All Wisdom” (Wikipedia) provides tables of confirmed and suspected provides tables of confirmed and suspected impact cratersimpact craters

http://en.wikipedia.org/wiki/http://en.wikipedia.org/wiki/List_of_impact_craters_on_Earth List_of_impact_craters_on_Earth

Impact Lakes in RussiaImpact Lakes in Russia

Many lakes in the interior of RussiaMany lakes in the interior of Russia7 show unusual features and may be 7 show unusual features and may be

impact craters, rather than karst, glacial, or impact craters, rather than karst, glacial, or other featuresother features

Understanding origins involves combining Understanding origins involves combining field observation, laboratory investigations, field observation, laboratory investigations, and statistical analysesand statistical analyses

NASA’s Jet Propulsion Laboratory NASA’s Jet Propulsion Laboratory provides much more information provides much more information

about impact craters throughout the about impact craters throughout the solar system in their “Welcome to solar system in their “Welcome to

the Planets” web sitethe Planets” web site

http://pds.jpl.nasa.gov/planets/http://pds.jpl.nasa.gov/planets/

Excellent information and classroom Excellent information and classroom activities have been created by the activities have been created by the Hawai'i Space Grant College, Hawai'i Hawai'i Space Grant College, Hawai'i Institute of Geophysics and Institute of Geophysics and Planetology, University of Hawai'iPlanetology, University of Hawai'i

http://www.spacegrant.hawaii.edu/http://www.spacegrant.hawaii.edu/class_acts/CrateringDoc.htmlclass_acts/CrateringDoc.html

Selected URLs about Impact CratersSelected URLs about Impact Craters

For more information/classroom activities:For more information/classroom activities:

http://www.solarviews.com/eng/edu/http://www.solarviews.com/eng/edu/craters.htmcraters.htmThe Meteor Crater home page: The Meteor Crater home page: http://www.meteorcrater.com/http://www.meteorcrater.com/A Webquest about impact craters: A Webquest about impact craters: http://earthview.sdsu.edu/trees/impact.htmlhttp://earthview.sdsu.edu/trees/impact.html