Two theories have been proposed to explain the formation of Grassy Lake. One attributes the formation of the swamp to earthquake; the other states that it is one of the many so-called oxbow lakes in the area. A study of aerial photographs showing the absence of fault zones and related sandblows tends to rule out any possibility of an earthquake origin, and in size and shape the swamp in no way resembles an oxbow lake. The aerial photographs reveal instead that the formation of the swamp was due to a natural levee being built up by a river which meandered through the low area now called Grassy Lake. The presence of dense stands of bald cypress (Taxodium distichum (L.) Richard), which grow in abandoned river channels, and a knowledge of the ecology of bald cypress support this hypothesis.
Huffman, Robert Terry
"Origin of Grassy Lake,"
Journal of the Arkansas Academy of Science: Vol. 28
, Article 12.
Available at: http://scholarworks.uark.edu/jaas/vol28/iss1/12