Make a Seismograph Science Project You may have heard of the Richter scale used to study earthquakes. In 1935 Charles Richter developed a system to measure the magnitude --or amount of energy released--of an earthquake. Each whole number on the Richter scale indicates a tenfold increase in amplitude (greatness in size). Thus, a 7.5 earthquake on the Richter scale actually has ten times the amplitude of a 6.5 earthquake. There is no upper limit on the Richter scale, meaning that it could be used to measure earthquakes of a ten or more magnitude if one ever occurred. The most devastating earthquakes we know of are 8 or 9 on the Richter scale. Scientists also measure seismic waves, or movements in the earth's crust. Fill a 2-liter soda bottle with water and use wire to suspend it about 1' above the surface of a table, using a sturdy stick or ruler set across stacks of heavy books. If it isn't confusing enough with so many things to measure, there's one more method for determining magnitude.
This Dynamic Earth--Contents [USGS] View of the planet Earth from the Apollo spacecraft. The Red Sea, which separates Saudi Arabia from the continent of Africa, is clearly visible at the top. (Photograph courtesy of NASA.) Ordering Instructions This book was originally published in paper form in February 1996 (design and coordination by Martha Kiger; illustrations and production by Jane Russell). U.S. or it can be ordered directly from the U.S. Call toll-free 1-888-ASK-USGS Or write to USGS Information Services Box 25286, Building 810 Denver Federal Center Denver, CO 80225 303-202-4700; Fax 303-202-4693 Version History Version 1.20 The online edition contains all text from the original book in its entirety. Linked Websites Please visit the Smithsonian Institution This Dynamic Planet website. See also This Dynamic Planet, the map showing the Earth's physiographic features, current plate movements, and locations of volcanoes, earthquakes, and impact craters.
Historic Earthquakes One person injured and extensive damage to roads and bridges. Structural damage occurred in the villages of Slana and Mentasta Lake, minor structural damage occurred at Fairbanks and items were knocked from shelves at Cantwell, Denali National Park, Glenallen, Paxson and Tok. Damage estimated at 20 million U.S. dollars. Some supports on the Trans-Alaska Pipeline were damaged and operation was suspended temporarily. Maximum intensity IX was assigned to areas where surface rupture occurred.
Sun-Earth Misconceptions A list of common and uncommon, famous and infamous misconceptions about solar-terrestrial physics... + Earth is closest to the Sun is the summertime or, it is warmer in summer because Earth is closer to the Sun False. This is by far the most common misconception about the relationship between Sun and Earth, one that is unfortunately perpetuated by lousy diagrams in most school textbooks. When someone says we are closer to the Sun in the summertime, do you ever remind them that while it may be summer in the northern hemisphere, it is wintertime in the southern hemisphere...and six months from now, the seasons and Earth's position will be reversed? In fact, in summer in the northern hemisphere, Earth is actually at its farthest point away from the Sun. Despite what you learned in school about Earth's "elliptical" orbit around the Sun, that elliptical orbit is pretty close to being circular (not the extended oval you see in most books). + The Sun does not rotate False. Bad Astronomy
Geologic Time: Geologic Time The Earth is very old -- 4.5 billion years or more -- according to recent estimates. This vast span of time, called geologic time by earth scientists, is difficult to comprehend in the familiar time units of months and years, or even centuries. How then do scientists reckon geologic time, and why do they believe the Earth is so old? A great part of the secret of the Earth's age is locked up in its rocks, and our centuries-old search for the key led to the beginning and nourished the growth of geologic science. Mankind's speculations about the nature of the Earth inspired much of the lore and legend of early civilizations, but at times there were flashes of insight. The evidence for an ancient Earth is concealed in the rocks that form the Earth's crust and surface. Contents || Next