Page:History of Southeast Missouri 1912 Volume 1.djvu/279

 HISTORY OF SOUTHEAST MISSOURI 219 tioii of the alluvial soil between the fissure and the stream bank moved in the direction of the stream and left a considerably larger fis- sure than would otherwise have been formed. All these fissures of both characters extend in the general direction of the earthciuake shocks. To understand their formation and also to account for the depth to which they extended, it must be remembered that practically all of the country affected by the earthquake is underlain at a depth of 10 to 20 feet by quick- sand and that over this quicksand is a coating of alluvial soil consisting at the top of loam and then of layers of sand and clay alternat- ing. The fissures opened out usually to the layers of quicksand, a depth of 10 to 20 feet. There are numbers of these fissures still to be seen. They have been partly filled by the action of the weather and by blowing in of leaves. When Lyell visited the New Madrid region in 1849 he saw a number of fissures still open, some of which he followed continuously for over a mile. They ranged in depth from five to six feet and from two to four feet in width. Lyell also saw' a fault produced by the earth- quake near Bayou St. John east of New Mad- rid, where the descent was eight to ten feet. Puller says that at Beechwell, northeast of Campbell in Dunklin county, is a fine fissure filled with sand. Pieces of lignite and shaly clay were seen in the trench, which appears to have been pvishecl diagonall.y upward into the clay alluvium, but not with sufficient force at least on one side, to break through.* He also gives an account of various fissures seen by him near Caruthersville, near Blythes- ville, and many of them across the Arkansas line. They are also to be seen east of the Mississippi river. These fissures in many cases were partly, if not entirely, filled. This was caused by the caving in of banks or walls and also by the pushing up of material from below. As the walls of the fissure opened, sand and water below the alluvium were pushed up, in some eases overflowed the walls of the fissure. It seems evident, too, that many of these cracks or fissures did not extend entirely to the sur- face of the earth but were stopped before reaching it. Into these cracks sand was forced up from below, filling the cracks and forming what geologists term a dike. These dikes are sometimes seen in the digging of wells or cellars and take the form of a narrow streak of sand pressed in between the other mate- rials. Thomas Beckwith of Charleston photo- graphed a remarkable dike of this character in Mississippi county, f Besides these fissures there were also formed what geologists term "faults" in the surface, though these were nothing like so common as the fissures. It was probably due to these that falls were formed in the Mississippi river, the faults running crosswise of the channel. Sev- eral accounts speak of these falls, some of them being as much as six feet in height and extending entirely across the river. No other effect of the earthquake has caused so much discussion or so wide a difference of opinion as that effect which geologists call ' ' warping, ' ' a term used to include the rising of part of the crust and the depression of other parts. The accounts given by several of those who witnessed the shocks speak of the uplifting of parts of the surface of the earth. In the accoimt of Mrs. Bryan it is said that the beds of some ponds were lifted up so that the ponds were drained and their former beds raised several feet. A. N. Dillard says : ' ' Previous to the earthquake keel boats would come up the St. Francois river and t U. S. Geological Survey, Bulletin 494, plate 3.
 * U. S. Oeolosrical Survey, Bulletin 404. p. .54.