Geo 365: Jan. 16, Day 16: Lignite

From the same spot as the last two days, a crumbling chunk of lignite. I interpret the sequence of yesterday's photo to be (from bottom to top) 1) a period of fairly intense ashy volcanism, with the ash washed into a lake by streams- it's clearly water carried, not ash fall; 2) a long period of quiescence,  with fairly deep water, allowing mostly pure diatomite to settle out- the clastic contribution during this time must have been very low; 3) shallowing water allowed colonization by reeds and other grass-like water plants. These died and accumulated to form peat, which has been compressed and lithified to lignite; 4) Another period of more active volcanism, apparently becoming more mafic at the top of the section shown in yesterday's photo. Today's sample is a fragment that fell out of step 3, so to speak.

Photo unprocessed. August 18, 2011. FlashEarth location (cross-hairs on pull-out). Lens cap is ~52 mm. If you choose to visit this spot, please see Monday's safety comments.