Mountains
Published on Feb 19, 2006 at 1:23 pm.
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Filed under Uncategorized, planets.
Continuing my random posts, I thought that I’d say a word or two about mountains. For some reason, I really like the mountains. Maybe growing up near the coast, they are something different. Maybe it is just the majesty of them, or something else. Whatever it is, I like mountains. So, back when I took a vacation, that was where I went. Fly Girl posted a couple of my photos on her blog, if y’all want to have a look.
Astronomers often site observatories on mountains. This is because the higher you are, the less air that you have to look through. The less air that you look through, the less atmospheric distortion that you have to deal with. Furthermore, some wavelengths of light, such as infrared, have trouble making it all the way down to sea level. However, infrared and millimeter wavelength radiation is more readily studied from the mountain tops. Even better would be to observe from space, but that is very expensive. One compromise would be to observe from an aircraft. NASA built an airborne observatory by placing a telescope in a C-141 Starlifter with a large hole cut in the fuselage for the 1 meter telescope to see through. This was named the
Kuiper Airborne Observatory (KAO). The KAO was did such wonderful work that a successor has been built called SOFIA. SOFIA is a 2.7 meter telescope carried in a modified Boeing 747-SP. If there is interest, I can blog about these later.Â
The mountains in my photos were the Rocky Mountains in Colorado. Like most of Earth’s mountains, they are created through plate tectonics. North America is slowly moving westward, and as it runs into another tectonic plate, the western portion of the North American plate is pushed upwards. On the other side of North America are some more mountains, but they were created by a plate collision long ago, and they are nowhere near as young as the Rocky Mountains, nor as tall. Some mountains are volcanic in nature. Many of the mountains in Washington and Oregon states are volcanic in nature. However, these are also associated with plate tectonics. As the North American plate pushes an oceanic plate under it, the ocean plate melts and works its way back upward, creating volcanos. Not all volcanos are formed in this fashion. The volcanos in Iceland are created by the two halves on the Atlantic Ocean pulling apart. This is also related to plate tectonics. The Hawaiian islands are also volcanic in nature, but they are created in a different manner. Here the Pacific plate passes over a hot spot in the Earth’s mantle. Volcanos form over the hotspot. As the plate moves past, carrying old volcanos away from the hotspot, they die and begin to erode, and new volcanos come to life more over the hotspot.Â
Other worlds also have mountains. Mars has the largest mountains in the Solar System, but plate tectonics has not built these mountains. Without active plate tectonics, hot spot volcanism becomes more important. These are the two mechanisms assisting in carring heat from the interior of a planet to its surface. Hot spots on Mars would be more active than on Earth, and without plate tectonics to carry volcanos from over the hot spots, these volcanos would just get bigger, and bigger. Mars is the home to Olympus Mons, the largest volcanic mountain anywhere in the Solar System. Venus also lacks active plate tectonics, so hot spot volcanos dominate there, too. Again, they grow very large, though not as large as on Mars. The volcanos on Venus are still active. Mars, being a smaller world, cooled off quicker than did Earth or Venus, so Mars is now ending its volcanic phase. The Moon also has mountains. However, the mountains on our Moon are formed in yet another different manner. Without plate tectonics or even hot spots (the Moon has neither), volcanism will not produce large mountains. Rather massive asteroid impacts have excavated large basins on the Moon. In some of the smaller basins, the ground has rebounded to form a mountain peak in the center of large craters. We see similar features in large craters all over the Solar System. APOD has a nice photo of the lunar crater Pythagoras showing a central peak. The largest basins on the Moon even cracked the crust, allowing lava to flow onto the surface from the lunar interior long ago before the Moon cooled off to where it could no longer support such volcanic activity. This volcanic rock, mostly basalts, is darker than regular lunar surface rocks, and this forms the basis of the dark markings on the Moon that we call “seas.” These basins are HUGE. Many of them are larger than some states. The edges of these basins are uplifted into mountain ranges. We also see similar features on Mercury.
So, there you have it. I’ve given a quick run-down on mountains in the Solar System.
Well, I can keep randomly coming up with topics to talk about, or some of y’all can give me suggestions. I have a couple of ideas coming up, so I might not get to your suggestions right away. You can send suggestions to rb200 at excite.com.
So, until next time,…
-Astroprof
