erratic

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erratic

a piece of rock that differs in composition, shape, etc., from the rock surrounding it, having been transported from its place of origin, esp by glacial action
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005

erratic

[ə′rad·ik]
(geology)
A rock fragment that has been transported a great distance, generally by glacier ice or floating ice, and differs from the bedrock on which it rests.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Hulterstadia cor and associated taxa, common in the Hulterstad Fauna of the erratic boulders on Oland, or related to it, occur in the Lelle section in the Fungochitina spinifera chitinozoan Zone, in the middle part of the Vormsi Stage.
It is now used as a standard procedure of determining exposure ages of erratic boulders and the respective moraines (e.g.
Freek Rhebergen (Emmen) discusses Baltic Ordovician sponges (Porifera) recovered from erratic boulders in Neogene fluvial deposits of The Netherlands and northern Germany.