University of South Alabama
ES 492: Science in the movies
Lecture 5: Geology of Meteorites
Presented by: Kourtney Crutcher
TODAY’S AGENDA
Geology of Meteorites
•
1. Meteorites: Comets and Asteroids
•
2. Geology of “Small Bodies”
•
3. Isotopic Impacts
•
4. K-T Extinction: A brief introduction
Figure: www.shewalkssoftly.com
METEORITES: COMETS & ASTEROIDS
Comet
Asteroid
A comet is a
conglomerate of gasses,
dust and ice.
An asteroid is an
inactive body of
rock material
A meteorite is a portion (meteoroid) of a comet or asteroid that has
successfully entered into the Earth’s atmosphere.
How small is “small?”
Small Body Defined
The largest “small body” that we have
recorded today is the asteroid Ceres. Ceres
has a diameter of roughly 1000 km that’s
approximately the distance from San Diego,
Ca to El Paso, Tx!
A small body, is a material with a much
lower escape velocity than that of a “large
body” such as the Earth. This is the main
distinguishing factor (Vereka, 1985).
Figure: www.usps.com
Escape Velocity
In Physics...
The minimum amount of speed needed for
an object to leave a body’s gravitational
pull is known as escape velocity.
Figure:
http://spiff.rit.edu/classes/phys301/lectures/black
_hole/black_hole.html
Geology of Small Bodies
Permafrost
Small bodies are majorly composed of
comets. Some asteroids are thought to be
the remnants of some comets that have lost
their ice over time. The sun can vaporize
the ice associated with comets and cause
venting if the nucleus is reached.
The manner in which the ice is contained is
similar to permafrost. Permafrost is soil that
remains at freezing temperatures for at
least two years (Vereka, 1985).
Figure: Buried basal ice from the Laurentide Ice Sheet
preserved as massive ice and icy sediments in
permafrost, NW Canada. (photo: Julian Murton)
Permafrost Outcrop
Buried basal ice from the Laurentide Ice Sheet preserved as massive ice
and icy sediments in permafrost, NW Canada. (photo: Julian Murton)
Figure: (Vereka, 1985)
Largest Impact Site in the US
Barringer Arizona
Just east of Flagstaff, Arizona this crater
lies two thirds of a mile in length and
approximately 50 feet in depth. The strata
has been overturned from the impact that
occurred (approximately) 50,000 years ago.
Sandstone, limestone, dolomite and
mudstone make up the sites stratigraphy
(Earth Impact Database, 2016).
Barringer Crater in Arizona, pictured, is the largest impact crater in the United States. It is
0.737 miles (1.186 kilometres) across and is believed to be about 50,000 years old. It is
thought to have been formed by a meteorite about 165 feet (50 metres) in diameter.
Photograph: Charles/O’Rear/CORBIS
Isotopic Impacts
An Overview
Research suggests that an overlap in the
dating of lava flows, meteorite impacts and
mass extinctions has made Isotopic data
problematic. However, Isotope
concentrations are significantly different in
meteors than that of the Earth’s crust as
seen in the K-T boundary layer (Glikson,
2005).
Figure: (Glikson, 2005)
Figure: http://theodoregray.com/
Figure: greenforecast.com
Artist: Ray Troll
Geologic Time Scale
The K-T Extinction
More accurately known as the CretaceousPaleogene extinction, this event has been widely
been accepted to be due to a meteorite impact.
This boundary marks the extinction of nearly 75% of
the earth’s plants and animals; Most notably, the
dinosaurs.
Iridium-bearing clay is characteristic of the K-T
boundary (only boundary rocks) regardless of
location.
Because meteorites have a much higher
concentration of Iridium than that of Earth, we
believe that the mass extinction event is largely
due to an asteroid approximately 10 km in diameter
(Cowen, 1994).
References
"Barringer". Earth Impact Database. University of New Brunswick. Retrieved 2016-1-24.
Cowen, R. 1994. History of Life. 2nd edition. 460 pp. Blackwell Scientific Publications, Cambridge, Massachusetts. This is
a freshman-level textbook published by Blackwell Science. Copyright Richard Cowen 1994. Available from Blackwell
Science, 238 Main Street, Cambridge, Massachusetts 02142, telephone 800-215-1000
Glikson, Andrew. "Asteroid/comet impact clusters, flood basalts and mass extinctions: significance of isotopic
age overlaps." Earth and Planetary Science Letters 236, no. 3 (2005): 933-937.
Veverka, Joseph. Planetary Geology in the 1980s. Washington, D.C.: Scientific and Technical Information
Branch, National Aeronautics and Space Administration, 1985. Accessed January 24, 2016.
http://history.nasa.gov/SP-467/ch7.htm.
Next Time
Deep Impact (1998)
MOVIE DISCUSSION
Think about the geology of meteorites,
their histories and geologic relationship
with the earth.