1. “How Did Those Rocks Get Up There? Exploring Lake Smerdyachee, Russia” Earth2Class Workshops for Teachers Lamont-Doherty Earth Observatory Originally presented 18 April 2015

2. Presented by Dr. Dallas Abbott Dr. Dallas Abbott LDEO Research Scientist LDEO Research Scientist dallas@ldeo.columbia.edu dallas@ldeo.columbia.edudallas@ldeo.columbia.edu

3. 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.

4. Some important concepts about impact craters Form when a bollide (meteorite, asteroid or comet) collides with a solid object (planet or moon) Form when a bollide (meteorite, asteroid or comet) collides with a solid object (planet or moon) Easily seen on our Moon, Mercury, and Mars, where weathering and erosion are slow Easily seen on our Moon, Mercury, and Mars, where weathering and erosion are slow Often hard to recognize on Earth because of the effects of weathering and erosion Often hard to recognize on Earth because of the effects of weathering and erosion

5. Meteor Crater (Barringer Crater) in Arizona was among the first recognized http://cass.jsc.nasa.gov/images/scraters/scraters_S10.gif

6. 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.Manicouagan CraterCanada http://antwrp.gsfc.nasa.gov/apod/ap001213.html

7. Many other craters have subsequently been identified, especially by remote sensing Approximately 190 are confirmed, with many other suspected Approximately 190 are confirmed, with many other suspected Mostly within the stable cratons of North America, Africa, Australia, and Europe Mostly within the stable cratons of North America, Africa, Australia, and Europe Earth’s greater gravitation pull probably means it has been hit more, but water, atmospheric weathering, and plate tectonics have destroyed or hidden many impact sites Earth’s greater gravitation pull probably means it has been hit more, but water, atmospheric weathering, and plate tectonics have destroyed or hidden many impact sites

9. High velocities at which meteoroids collide with Earth explain the great effects from even small objects Velocities range between 11.2 km/sec (escape velocity from Earth) and 72 km/sec (orbital velocity of Earth plus escape velocity of solar system) Velocities range between 11.2 km/sec (escape velocity from Earth) and 72 km/sec (orbital velocity of Earth plus escape velocity of solar system) Kinetic Energy released is proportional to square of velocity Kinetic Energy released is proportional to square of velocity Effects is that meteorites are, gram for gram, more than 100x as powerful as TNT! Effects is that meteorites are, gram for gram, more than 100x as powerful as TNT!

10. Methods to identify impact locations include: Siderophile elements (esp. Ir, Os, and Pt) in “impact melt rocks” Siderophile elements (esp. Ir, Os, and Pt) in “impact melt rocks” “Shock metamorphism” in “target rocks” and minerals “Shock metamorphism” in “target rocks” and minerals “Shatter cones” “Shatter cones” High-pressure mineral phases, such as stishovite High-pressure mineral phases, such as stishovite “Diaplectic glass” and tektites in “ejecta blankets” “Diaplectic glass” and tektites in “ejecta blankets”

11. Many craters or remnants have been recognized by the presence of rare elements “Siderophile elements” such as Ir indicate that terrestrial clays have been mixed with extraterrestrial materials “Siderophile elements” such as Ir indicate that terrestrial clays have been mixed with extraterrestrial materials One of the best studied is the subsurface Chicxulub structure in Mexico, widely accepted at the location of the Cretaceous- Tertiary boundary event One of the best studied is the subsurface Chicxulub structure in Mexico, widely accepted at the location of the Cretaceous- Tertiary boundary event

12. 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

13. Impact Craters are classified as “Simple” or “Complex” “Simple Craters” are relatively small, have a smooth bowl shape, and a depth:diameter ratio of 1:5 to 1:7 “Simple Craters” are relatively small, have a smooth bowl shape, and a depth:diameter ratio of 1:5 to 1:7 “Complex Craters” are largely and show the effect of gravitational collapse of the walls to produce a central peak or peak ring “Complex Craters” are largely and show the effect of gravitational collapse of the walls to produce a central peak or peak ring

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

16. What might happen when an impact occurs in the ocean? Tsunami! A tsunami is a giant sea wave or series of waves caused by disruption of the ocean surface A tsunami is a giant sea wave or series of waves caused by disruption of the ocean surface Most tsunamis are connected with earthquakes or volcanic eruptions, but some may be caused by meteorite or asteroid collisions Most tsunamis are connected with earthquakes or volcanic eruptions, but some may be caused by meteorite or asteroid collisions For more information about tsunamis, go to http://www.geophys.washington.edu/tsunami/wel come.html For more information about tsunamis, go to http://www.geophys.washington.edu/tsunami/wel come.html http://www.geophys.washington.edu/tsunami/wel come.html http://www.geophys.washington.edu/tsunami/wel come.html

17. Where Are Impact Craters Found? The “Fount of All Wisdom” (Wikipedia) provides tables of confirmed and suspected impact craters http://en.wikipedia.org/wiki/List_of_impact_cr aters_on_Earth http://en.wikipedia.org/wiki/List_of_impact_cr aters_on_Earth

18. Impact Lakes in Russia Many lakes in the interior of Russia Many lakes in the interior of Russia 7 show unusual features and may be impact craters, rather than karst, glacial, or other features 7 show unusual features and may be impact craters, rather than karst, glacial, or other features Understanding origins involves combining field observation, laboratory investigations, and statistical analyses Understanding origins involves combining field observation, laboratory investigations, and statistical analyses

20. NASA’s Jet Propulsion Laboratory provides much more information about impact craters throughout the solar system in their “Welcome to the Planets” web site http://pds.jpl.nasa.gov/planets/ http://pds.jpl.nasa.gov/planets/

21. Excellent information and classroom activities have been created by the Hawai'i Space Grant College, Hawai'i Institute of Geophysics and Planetology, University of Hawai'i http://www.spacegrant.hawaii.edu/class_acts/ CrateringDoc.html http://www.spacegrant.hawaii.edu/class_acts/ CrateringDoc.html

22. Selected URLs about Impact Craters For more information/classroom activities: http://www.solarviews.com/eng/edu/craters. htm http://www.solarviews.com/eng/edu/craters. htm http://www.solarviews.com/eng/edu/craters. htm http://www.solarviews.com/eng/edu/craters. htm The Meteor Crater home page: http://www.meteorcrater.com/ The Meteor Crater home page: http://www.meteorcrater.com/ http://www.meteorcrater.com/ A Webquest about impact craters: http://earthview.sdsu.edu/trees/impact.html A Webquest about impact craters: http://earthview.sdsu.edu/trees/impact.html http://earthview.sdsu.edu/trees/impact.html