Posts tagged geology
Posts tagged geology
Bowling Ball Beach - Schooner Gulch State Beach, California
At the edge of the Pacific Ocean, the beach at Schooner Gulch State Beach near Mendocino, looks as though its been scattered with oversized bowling balls. Almost perfectly spherical, stones like these have caused wild speculation wherever they’ve been discovered, with answers from aliens to dinosaurs, but the answer is actually simple geology.
Best observed at low tide, the so-called bowling balls are actually a geological phenomena known as “concretion”, sedimentary rock formed by a natural process wherein mineral cements bind grains of sand or stone into larger formations. These boulders are the result of millions of years of concretion and erosion, exposing the hard spheres as the mudstone of the cliffs receded around them.
Rutile Quartz cluster
I don’t know if it’s the titanium (rutile is TiO2) or the fact that rutile has an incredibly high refractive index (giving it an adamantine luster), but I really do love rutile.
Columnar basalt along the Yellowstone River, Yellowstone National Park, Wyoming
Photo by Clif Doyal -2004
From Earth Science Picture Of The Day; January 17, 2014:
Photographer and Summary Author: Ryan Miller
The photo above shows a portion of the Tongariro Alpine Crossing mountain trail on the North Island of New Zealand. This crossing stretches across the Tongariro volcanic complex on the North Island’s Central Plateau. Seen in the background at left center is Mount Ngauruhoe, a parasitic stratovolcano rising to a height of about 7,500 ft (2,290 m). In the Lord of the Rings Trilogy, Mount Ngauruhoe was featured as Mt. Doom. The crossing is approximately 12 mi (19 km) in length and normally takes about seven hours to complete. Photo taken on March 29, 2011.
Ice formations in sand reveal the creation of the Grand Canyon.
Along Lake Michigan, freezing has created sand formations that resemble the way that erosion works in natural canyon structures, only in miniature. Reason #1001 why geology is amazing!
(reddit user SAT0725)
For the geologists in the house, the “slippery clay” is mostly smectite. Several groups presented new lab studies of friction in similar smectite mixtures at the AGU fall meeting. Also, the temperature data from this expedition is interesting, but that will get its own post later.
AGU Fall Meeting, largest worldwide conference in geophysical sciences, with nearly 20,000 Earth & space scientists, educators, students, & policy makers.
Watch out San Francisco; her we come!!!
Keep the beer flowing and never mind those people stopping suddenly on the sidewalk to stare at the stone tiles on the sides of buildings. We’re just admiring the gneiss texture.
Uvarovite Garnets - Russia
Yes, garnets can be green. Uvarovite is a Calcium Chromium silicate with the usual garnet crystal structure. I’m still looking for some crystals large enough to add to my minerals-that-look-like-dice collection, but have yet to see any sizable specimens outside of a museum or university collection. Does anyone have any suggestions?
Pyrite Suns on Shale - Illinois