In the text book on page 238, there is a definition for the word "liquefaction". Could someone explain this a little better for me. And is this something I need to know?

-- Katie France (loki2cute@yahoo.com), April 07, 2001

Answers

Liquefaction is a process that affects water saturated sediments before they have undergone lithification (i.e. turned from soft sediments to hard rocks). Liquefaction commonly affects rapidly deposited sands, which have unstable grain packing arrangements. When these sands are shaken (e.g. by an earthquake) or loaded by another depositional event, a rise in pore-fluid pressure occurs and the water tries to escape and the grains become momentarily suspended in the pore fluid-i.e. the sediment is liquefied. Liquefaction can be described as a process where a solid temporarily behaves in a liquid-like fashion. An important implication of this is that if the deposited sands have any structures within them they will deform during liquefaction. Deformed sedimentary structures in ancient rocks can tell you something about the history of that rock and hence may allow you to make an interpretation about the environment at or near the time of deposition. In the case of liquefaction related structures, you could for example suggest they indicate a seismically active environment at or near the time of deposition. If you want some more detailed information have a look at a paper by Lowe, D. 1975 in Sedimentology on water escape structures

-- Nick Lee (nick_lee@anadarko.com), April 10, 2001.