MinuteEarth explains why rivers curve. Understanding water movements allow scientists to recreate ancient environments and even help to predict fossil localities.
When hiking a steep 1,700ft+ trail at High Point State Park among the backs of the Valley and Ridge mountains, I encountered an outcrop of Needle Ice by accident. Making my way up over some boulders, I stepped on a ledge of soil and a section fell off, revealing what first appeared to be glittering icicles embedded in the soil.
This occurs when the surface air temperature is colder (below 0 °C) than the temperature of the ground soil (above 0 °C) – or when the warm soil air meets the cold surface air. Because of these contrasting temps that causes molecular attractions, groundwater is pulled up to the surface via capillary action and then freezes into long, needle-like ice structures.
Here are 2 macro close up photos I snapped. For scale, the centered Needle Ice is roughly 17mm across, or about the size of an American dime.