Flying over Greenland

On the plane from Heathrow to San Francisco, Nils and I sat across the aisle from an Icelandic glacial geologist on his way to vacation to Hawaii. When we flew over the east coast of Greenland I had to wake Nils up and make him look out the window! So amazing.

Medial moraines where two glaciers flow together:


A beautiful long fjord:

Tidewater glaciers calving

Field of bergs:

Winners

The Art of Subduction took 3rd place at the annual Geological Society of South Africa Western Cape Branch Quiz night.

Nice job team.

Fun with Folds

BrianR at Clastic Detritus posted a great photo of some disharmonic folds in bedded strata. Here are some more!


I particularly like the chocolate-tablet layers visible on the top of this outcrop.

Rock of the Week #10

1. What are the sedimentary structures in this rock?
2. What can they tell you about the depositional environment?
3. Why is this rock reddish in colour?




Solution to Rock of the Week #9:

This is a SKARN – that is, a contact metamorphic rock produced when magma intruded low-grade country rock. This sample comes from the Birch Creek Pluton in the White-Inyo Mountains of California. The older rock here was a Cambrian (530Ma) carbonate and shale marine platform sequence. The intrusion of granitic plutons (80Ma) transferred heat and Si-rich fluids into the sedimentary rocks, causing metasomatism and metamorphism. This was a moderate-sized pluton and the zone of contact metamorphism around it is about 600m thick. This sample was taken ~200m from the pluton where temperature reached about 500°C. It contains garnet, dolomite, calcite, fluorite, epidote, and quartz and is classified as a Ca-Fe-Si skarn.


1. (1 pt) 2 minerals?
: 1 point if 2 of the above listed minerals are given.

2. (1 pt) Rock name?
: 1 point for skarn (only).

3. (2 pt) How did it form?
: 1 point for contact metamorphism or metasomatism.