Sand Blow — Missouri, Arkansas, Tennessee, Kentucky
Sand blows occur throughout the New Madrid Seismic Zone (NMSZ) wherever there is a shallow water table, deep unconsolidated sands, and a thin capping overburden. They are found throughout the "Bootheel" of Missouri, northeastern Arkansas, northwestern Tennessee, and southwestern Kentucky. (from Obermeir, United States Geological Survey).
During the winter of 1811-1812, approximately 2,000 major earthquakes shook the NMSZ of central North America, including at least three, possibly four, great catastrophic earthquakes having magnitudes exceeding 8 (Richter magnitude).
These major earthquakes of 1811-1812, and major earthquakes occurring throughout the past, caused sand geysers to erupt from the ground.
Sand Blow — Eyewitness Accounts
“…about sunrise another very severe one came on, attended with a perpendicular bouncing that caused the earth to open in many places.. . the deepest I saw was about twelve feet. The earth was, in the course of fifteen minutes after the shock…entirely inundated with water. The pressing of the earth, if the expression be allowable, caused the water to sprout out of the pores of the earth, to the height of eight or ten feet! The agitation of the earth was so great that it was with difficulty any could stand on their feet, some could not — the air was strongly impregnated with a sulphurous smell.”
Johnston, Arch C. and Eugene S. Schwieg
1996 The Enigma of the New Madrid Earthquakes of 1811-1812. United States Geological Survey and CERL. The University of Memphis: Memphis Tennessee. http://www.cr.nps.gov/delta/volume2/natural.htm
“In all the hard shocks mentioned, the earth was horribly torn to pieces - 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 this country, some of which closed up immediately after they had vomited forth their sand and water, which it must be remarked, was the matter generally thrown up. In some places, however, there was a substance somewhat resembling coal, or impure stone coal, thrown up with the sand. It is impossible to say what the depths of the fissures or irregular breaks were; we have reason to believe that some of them are very deep.”
-- Eliza Bryan, March 22, 1816
Lorenzo Dow's Journal, Published by Joshua Martin, Printed by John B. Wolff, 1849, on pages 344 - 346.p
Sand Blow Radargram — Dyer County, Tennessee
Radargram cross section of a sand blow. Deformation caused by
subsurface collapsing into region of ejected sands following eruption. Bowl shape
will hold water if
dike exits at higher elevation. Width of depression is approximately 50
meters. Depth is approximately 3.5 meters. -200-MHz GSSI Antenna-
Excavated Sand Blow — Trench Sides Rapidly Collapse
Excavated sand blow using a backhoe. The sides of the original elongated, narrow trench rapidly collapse to form a circular depression. Water rapidly flows into trench from subsurface channels and fills depression.
Sand Blow — Both Water Source and Drain
Sand blow in corn field within a river bottom near the Obion River with rising water table from storm event upstream. Water is flowing from the rising water table through the dike onto the surface. Note dark area near center of pool. Water both rapidly enters and exits the sand blow depending upon the water table elevation.
Sand Blow — Excavated
Sand blow showing sand dike, vent, and cone backfill. The sand dike is not round, but an elongated fissure that runs 200 ft before tapering at both ends. The fissures of all the sand blows in the field run parallel, and at first thought likely due to the bearing toward the earthquake's epicenter. However, a report by the USGS (Obermeier, 1989) stated:
The orientation and intensity of long fissures (greater than 0.8 km) are largely controlled by very localized geologic and topographic factors; in meander-belt and braided stream alluvial deposits, where concentrations of fissures are greatest, the orientation is generally parallel to former stream channels and has no relation with the probable direction of shaking.
The sand dike is also exposed at the opposite side of the trench, behind the photographer.
Sand Blow — Survey Traverse
Locating sand blows in a 100-acre field required 10 to 15 ft spacing on survey traverses. Survey time was approximately 8 hrs when traveling at 5 mph. (All values are approximations.)