A tale of two squishies and modern art

Rocks usually seem to be permanent, solid fixtures on the Earth, but occasionally I come across a rock that blurs the line between solid and liquid. These rocks preserve fluid-like behavior in crystalline form and can envoke a sense of abstract expressionism, perhaps reminiscient of a Jackson Pollrock painting (I'm so sorry). Today's rocks come from islands on opposite ends of the U.S. - Antelope Island in Utah and Vinalhaven in Maine.

Antelope Island juts out into the south end of the Great Salt Lake in Utah. In addition to holding evidence of isostatic rebound (due to the draining of Lake Bonneville), Antelope Island is home to a type of rock called a migmatite. Part metamorphic and part igneous, migmatites form when a metamorphic rock like a gneiss is submitted to high temperatures and high pressure. The high temperatures weaken the rock and causes a little bit of melting, and the high pressure squishes the minerals into a tapestry of swirls. If you're interested in numbers, this paper reports that the migmatites of Antelope Island reached a temperature of 1300-1450 F (700-785 C) and a pressure as high as 400 MPa. To put the pressure into perspective, if the pressure is just due to being buried, these rocks would have been about 7.5 mi (12 km) below the Earth's surface!

Migmatite (1m wide), Antelope Island UT

Vinalhaven, an island off the coast of Maine, is home to a solidified magma chamber (here's a description of the geologic history). After cooling and solidify, subsequent erosion and tectonic rotation now allows us to walk across a magma chamber from top to bottom and observe many examples of magma frozen in the act of flowing. The rock in the photo below captures two magmas of different viscosities coming in contact. When two immiscible fluids (fluids that can't mix) contact each other, an instability called viscous fingering can arise, resulting in fingers of the less viscous fluid reaching into the more viscous material.

Magma mixing preserved in a solidified magma chamber, Vinalhaven ME

Rocks like these are nature's canvases. Even after the paint dries, some essence of motion is captured. From that motion, we can understand aspects of a rock's origin or simply appreciate the brush strokes in an abstract sort of way.