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==Fossil evidence== The fossil evidence of fire comes mainly from charcoal. The earliest charcoal dates to the Silurian period. Charcoal results from organic matter exposed to high temperatures, which drives off volatile elements and leaves a carbon residue. Charcoal differs from coal, which is the fossilised remains of living plants and burns to leave soot. Fossil charcoal is known as fusain, a crumbly silky material which may form blocks or microscopic films. Plants can be preserved in exquisite detail, and original cell structures can often be preserved in three dimensions.〔 Spectacular images can be recovered using scanning electron microscopy. Fragments can be distributed some distance, and soot-rich layers in strata deposited by deltas can provide a 'time-averaged' record of fire activity in the catchment (and up-wind) area of the river.〔 The loss of volatile elements during combustion means that charred remnants are usually smaller than the original organism, but this same factor makes them unlikely to be eaten by any animals (for they have no nutritional value), enhancing their preservation potential.〔 Evidence of lightning strikes is usually difficult to link to specific fires; occasionally they may scorch trees, but fulgarites - fused sediments where soil has been melted together by a strike - are occasionally preserved in the geological record from the Permian onwards.〔 Scorched layers of trees which survived fires can also provide evidence of fire frequency - especially as they can be related to the annual growth rings of the affected tree. These are useful for relatively recent times, but there are only putative reports of this phenomenon in pre-Tertiary strata.〔From a Triassic tree in Antarctica〕〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Fossil record of fire」の詳細全文を読む スポンサード リンク
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