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If you grew up on the moon, would your bones be heavier or lighter than they are now?
The gravitational field of the Moon is only about 1.6 m/s2, compared to 9.8 m/s2 on Earth. This is about
1/6th as strong. The effect on our physiology is significant, especially for bones, which have developed on
Earth in response to our gravity. Without this gravity (or with it largely diminished), bones begin to lose
mass. Astronauts experience many issues from extended periods in a zero-g environment, and bone loss is
perhaps the most serious. A rule of thumb is that one day in space requires one day of recuperation once
back on Earth, but for bone loss its even more severe, requiring months to return to normal.
If a human were to grow from childhood to adulthood in such an environment, we can only imagine what
the overall effects on his/her physiology would be. It’s almost certain that her skeletal structure would be
much smaller. Perhaps she would grow much taller, but with very long and narrow bones. The key is that
the weight is so much less that the structural requirements of the bone are greatly reduced, and our bones
grow in response to this stimulus of stress. So with that removed, they would likely be much less sturdy.
Where are the tallest and longest mountain chains on Earth? How were they formed?
The tallest mountain chain is the Himalaya’s. This Asian chain includes the highest peak on Earth, Mount
Everest. The Himalayas include more than one hundred peaks over 7,200 m high. The range extends over
2,400 km and was formed from the subduction of the Indian tectonic plate under the Eurasian plate.
The longest mountain range in the world is the Andes, which extends over 7,000 km along the west coast of
South America, from southern Argentina to Venezuela. At over 6900 m, Mt. Aconcagua is its highest
peak. The Andes were formed by Nazcan and Antarctic tectonic plates being subducted underneath the
South American Plate.
However, if we want to include undersea mountain ranges, then the mid-ocean ridge system becomes the
longest mountain range in the world, stretching several times longer than the Andes.
How do we know that tectonic plates move?
Today, we can use GPS to measure the relative separation of locations on the surface of the Earth. These
measurements allow us to track movement even as small as millimeters per year. Mapping out these
motions clearly shows the aggregate motion of the underlying plates.
Describe how transform plate boundaries differ from plate boundaries.
Transform Plate Boundaries are locations where two plates slide past one another. They lack the dramatic
compressive or tearing forces associated with convergent or divergent boundaries.
What form of geologic activity is exhibited along transform boundaries?
Transform boundaries exhibit earthquakes associated with the sliding of the two plates, often resulting in
long valleys and other linear features.
On what tectonic plate do you live?
I live on the North American plate.
How many adjacent plates are there to the one you live on?
Adjacent to the North American Plate is: the Pacific, Juan de Fuca and Eurasian plates on the west; the
Cocos, Caribbean and South American plates to the south; the African and Eurasian plates to the East.
Note the Eurasian plate borders on both the east and west!
In which direction are these plates moving?
Generally, the North American plate is moving to the southewest, away from the mid-Atlantic ridge. Thus
it is diverging on the east from the Eurasian and African plates. On the southern and western borders, the
Pacific, Juan deFuca, Cocos and to some degree the Caribbean plates are subducting under the North
American plate. Certain segments, such as the San Andreas fault in California, are transform boundaries.
If the Mid-Atlantic Ridge opens up at the rate of 5 centimeters per year, how much farther apart will Paris
and New York be in 1,000 years (please show your calculations)?
5 cm/yr × 1000 yrs = 5000 cm = 50 m
Mount Everest is now approximately 8,850 meters tall, and it has been growing taller at a rate of about 2
centimeters per year. Estimate the approximate age of the mountain.
8850 m ×100 cm/m
= 442,500 yr
2 cm/yr
Where is New Horizons space probe heading and where is it right now?
New Horizons is a NASA spacecraft launched in 2006 and headed for Pluto and the outer reaches of our
solar system. It has now passed the orbit of Uranus, and is about 26 AU from the Sun. It will reach Pluto
in 2016.