Talc-actinolite schist in thin section Images by author
Tag: original
<3 Geology
Heart-shaped greenschist facies pillow basalt from Ely, Minnesota.
Banded Iron Formation, Soudan
Some absolutely gorgeous ~2.7 Ga Banded Iron Formation (BIF) from Soudan, Minnesota. The rotating silver and reddish layers are hematite and jasper respectively, and these BIFs differ from their Proterozoic counterparts in that they were chemically precipitated. The outcrop is intensely folded and shows numerous interference patterns, meaning that there are folds that have been… Continue reading Banded Iron Formation, Soudan
Pegmatite
Red Ace Pegmatite (WI); Lithium feldspar with pink tourmaline
Welded Tuff
Welded tuff is a type of pyroclastic rock. A pyroclastic deposit consists of fragmented material that is formed from explosive volcanic activity or from aerial expulsion from a volcanic event. These pyroclasts may be deposited in the form of pyroclastic flows [a dense, ground-hugging cloud of ashy material], forming ignimbrites (Greek for “fire cloud material”).… Continue reading Welded Tuff
Flow-banded rhyolite
Rhyolite is an igneous, extrusive volcanic rock high in silica forming typically in continental arc settings. The flow-banding in this sample is caused by the friction of the viscous magma in contact with a solid rock surface or by compaction, causing flattening and welding of shards and pummice. [Be prepared for pictures of a bunch… Continue reading Flow-banded rhyolite
Art of Geology
As a geologist, not only do you have to be good in math, chemistry, physics, history, and writing, but you also kind of need to be decent at art. These are thin sections of magmatic rocks with my accompanying petrographic sketches. For a relatively small little circle, these guys take a really long time to… Continue reading Art of Geology
Dunite
Thin section of dunite under XPL. Dunite is a type of peridotite that contains over 90% olivine and may either be found in ophiolitic complexes or xenoliths in basalt lavas. Note the ‘bubble’ texture of the vibrant birefringent olivine grains at the top and bottom of the image, and the serpentine (gray and white) and… Continue reading Dunite
Pieces of the Moon!
Thin sections of lunar basalt (3.15-3.35 Ga) viewed under plane polarized light and cross-polarized light. Sample contains olivine, clinopyroxene, and plagioclase. Images by author
Highlights of the Phanerozoic: Part 3 – Cenozoic [65 Ma – on]
Here’s a few highlights from the history of the Earth and life during the Cenozoic Era, the third of the Phanerozoic, which is the fourth Eon in Earth’s history. These events are mainly focused on North America, and the dates of Periods and Epochs are partially rounded. CENOZOIC (CZ) [65 Ma – on] PALEOGENE (PE)… Continue reading Highlights of the Phanerozoic: Part 3 – Cenozoic [65 Ma – on]
Emily Zawacki, Ph.D. 