Field observations has also been an important ingredient in understanding the growth of terraces by precipitation from a fluid flow. Such terraces are known around the world where there is warm, mineral rich water coming out of the ground and flowing onto the Earth's surface. We have recently observed similar terraces forming on ice covered rivers with a thin layer of flowing water on top. The main question is: why does the material (ice, calcium carbonate, silicate) solidify/precipitate in a pattern with terraces that are similar from the millimeter to the meter scale? Our field studies have concentrated on studying the fluid and precipitate chemistry~~\cite{Hammer2005a,Jamtveit2006a}, quantify the geometries and study the fluid flow~~\cite{Hammer2007a}. The insights from the field work are used to guide the experimental setups to reproduce terraces of calcium carbonate, salt and ice. After several failed attempts we were the first to succeed in reproducing travertine growth patterns in the lab and quantitatively compare to simulation results~\cite{Hammer2008a}. Travertine (or tufa) is an important rock type economically (the facade of ``Realfagsbygningene'' at NTNU are covered by travertine), for the study of climate history and the hot pools formed by the terraces host a vast niche of high temperature organisms that have been studied intensively the later years. Our explanation of the terrace pattern as a purely physico-chemical process as opposed to being biologically controlled is important to interpret the role of biology and inorganic processes in these environments~\cite{Hammer2010a}.

I enclose the following document: \begin{itemize} \item {\rm Hammer, {\O}., Dysthe, D.K., Lelu, B, Lund, H. Meakin, P., Jamtveit, B.,} \newblock {\em Calcite precipitation instability under laminar, open-channel flow\/}. Geochimica Et Cosmochimica Acta {\bf 72}, 5009 (2008). \end{itemize}