EARTHQUAKES! Sand Boils & Liquefaction-EC** EarthCache
EARTHQUAKES! Sand Boils & Liquefaction-EC**
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As an earthcache there is no container to find, instead you will learn something about the geology of this area. Please e-mail to my profile the answers to the following questions. PLEASE send the answers BEFORE U log the 'find' -----THERE R TWO (2) EARTHCACHES AT THIS SITE
QUESTIONS: 1- To understand how unstable 'liquifaction' makes the ground-- Put some sand into a medium sized plastic container. Place a medium sized rock on top of the sand, then gradually saturate the sand with water. Now strike the container sharply several times--Describe what happens to the rock. 2- Looking to the southeast (of the posted coordinates) you see a large mound which is the remains of a 'sand blow' which is also called a 'sand boil.' Notice that the large fields to the west, east and north are flat---ESTIMATE THE HEIGHT OF THIS ELEVATED MOUND. (east is towards New Madrid) 3- Choose the size of this 'sand boil' A- small(volume of an auto) B- medium (volume of a small house) C- large (volume of a baseball field) 4- Submit a pic if you choose. -----Did U get the other earthcache at this site tooooo??? 5. There is another earhcache at this site--check it out! GC4FEVB** USE THE FARM ACCESS ROAD to get closer to the 'sand boil' if you wish.But DO NOT go into the field ! There is a turn around at the end of the road--good weather only! THANKS FTDiscover: McRob&2hero's * * * * * * * * * * * * * After consultation with some local residents and farmers, I was directed to this location as the site of what is often called a 'sand boil.' The information that follows is an effort to explain how they occur. This location is a part of what is called the Bootheel Fault which has some of the most visible 'sand boils' in the entire region. On December 16, 1811, an earthquake estimated at a magnitude of about 8.0 on the Richter scale shook the small town of New Madrid, MO. It was the first of three powerful earthquakes that would shake the central Mississippi River Valley that winter. Survivors of the quakes reported not only intense ground shaking and land movement, but also an unfamiliar phenomenon--water and sand spouting up through fissures, or cracks, in the earths surface. In a letter, New Madrid resident Eliza Bryan wrote in 1816 that, "...the surface of hundreds of acres was, from time to time, covered over in various depths by the sand which issued from the fissures, which were made in great numbers all over the country, some of which closed up immediately after they had vomited forth their sand and water." Geology: Modern earthquate researchers refer to this expulsion of water and sand from the ground as 'earthquake dewatering,' which results from liquefaction. Normally, water fills the spaces between the sand grains, but the grains are still touching and friction holds the sand together as a unit--but liquefaction increases the water filled spaces between the grains, allowing it to flow like liquid. Liquefaction occurs when an earthquake vigorously shakes and then compacts the water-saturated sediments. As the compression process dispalaces the water between the sediment pores,-- water and sand shoot upward and out of the ground. Imagine a cube full of sand and water. If you press it in from both sides, compressing and releasing it, then compressing it again, you build up what is called pore-water preasure, according to the US Geology Survey. "It is like shaking a coke can--when the preasure builds up and you release it, the fluid comes shooting to the surface," reports Martitia Tuttle a consultant, "These fountains of water & sand can sometimes shoot as high as 30 feet into the air," she reports. Sand boils are what remains--large mounds of sand which have eroded over time and are often put under cultivation. Geologists study them to help understand the geological past -- because they know that the 1811-12 New Madrid earthquakes were not geological flukes--similar events had repeatedly occurred here in the geological past. THERE ARE TWO (2) EARTHCACHES AT THIS SITE-Did U get the other one tooo!!! ******* More info on earthquakes: animations-- http://www.iris.edu/gifs/animations/faults.htm The New Madrid earthquake included the third type. There were about 2,000 after shocks as well! Check-out: GC2M5B New Madrid Earthquake Mystery cache for more information on the earthquakes of 1811-12 Not all those who wander are lost--This is my 36th of 45 published earthcaches
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