Pictures of the Week 3.20.14

Somewhere in North Cascades National Park late summer 2004. 

Somewhere in North Cascades National Park late summer 2004. 

Somewhere in North Cascades National Park late summer 2004. 

Somewhere in North Cascades National Park late summer 2004. 

Somewhere in North Cascades National Park late summer 2004. 

Somewhere in North Cascades National Park late summer 2004. 

Mount Baker/Snoqualmie National Forest summer 2009. The white lines of quartz you see in the rock are called dikes and sills. These are formed deep under the earth's crust when superheated water is injected or is intruded into cracks in the rock under high pressure. Silica and probably other minerals and compounds dissolved in solution in the superheated water precipitate out in the cracks, filling them and forming quartz deposits. This is how veins of other more valuable minerals like gold, silver, copper etc. are formed as well. Sills are usually horizontal and follow the bedding planes of the surrounding rock. Dikes are usually vertical and cut across the bedding planes of the surrounding rock. Dikes are usually fed by sills. The rock in the North Cascades is often so folded that you can't be sure the deposit you are looking at is in its original position when formed. Many deposits formed as sills are now vertical and vice versa for dikes. In addition to all this, the rock in these photos has been rounded and worn smooth by streamflow.