Here’s a few highlights from the history of the Earth and life during the Mesozoic Era, the second Era of the Phanerozoic, which is the fourth Eon in Earth’s history. These events are mainly focusing on North America, and the dates for Periods and Epochs have been partially rounded. MESOZOIC (MZ) [251 – 65 Ma]… Continue reading Highlights of the Phanerozoic: Part 2 – Mesozoic [251 – 65 Ma]
Tag: original
Highlights of the Phanerozoic: Part 1 – Paleozoic [542 – 251 Ma]
Here’s a few highlights from the history of the Earth and life during the Paleozoic Era, the first Era of the Phanerozoic, which is the fourth Eon in Earth’s history. These events are mainly focusing on North America, and the dates of Periods and Epochs are partially rounded. PALEOZOIC ERA [542 - 251 Ma] CAMBRIAN (Є)… Continue reading Highlights of the Phanerozoic: Part 1 – Paleozoic [542 – 251 Ma]
A tale of two CaCO3’s — Calcite and Aragonite
Aragonite (left) and calcite (right), both CaCO3; image by author Here in this photo, we clearly have two different minerals–one aragonite and the other calcite. However, they both have the same chemical formula of CaCO3. So how can it be that these two different minerals are both calcium carbonate? Aragonite and calcite are polymorphs of… Continue reading A tale of two CaCO3’s — Calcite and Aragonite
Rhodochrosite
Rhodochrosite - MnCO3 The Alma King, largest known rhodochrosite crystal; state mineral of Colorado. Specimen from Denver Museum of Nature and Science; photo by author
What are these things? — Stylolites
See these thin little squiggly gray lines in the rock in the photo above? These are what you call stylolites. Stylolites are caused by pressure dissolution, meaning that a large amount of stress was applied to the rock in a direction perpendicular to which to stylolites are formed. Because of this pressure applied, there’s a dissolving… Continue reading What are these things? — Stylolites
Words to know: Palimpsest
On my very first ever day of geology class, my geology professor introduced me to the word palimpsest, which is a text written over other texts. Normally the word is used to describe parchments in which the original writing has been removed and written over by new writing, However, the Earth itself truly is the ultimate… Continue reading Words to know: Palimpsest
Barite
Barite - BaSO4 Barite, is a common hydrothermal mineral. It may also be deposited by cold groundwater solutions. The crystallization is orthorombic. Quite commonly, as in this specimen, crystals are flattened parallel to the basal pinacoid, and terminated on the edges by prism faces. Cleavages parallel both the base and the prism. Lawrence University collection, information… Continue reading Barite
Oolitic limestone
Limestone with ooids and shells, viewed through a hand lens
Common minerals to know
Here are some common minerals whose names and formulas are good to know, along with some of their properties! (In rows, left to right; H=hardness, tested in lab using Mohs hardness scale) 1) Halite (NaCl) – H=3.5; it tastes salty! (yes, lick it) 2) Fluorite (CaF2) – H=4; ranges from transparent, to purple, to blue 3) Sylvite… Continue reading Common minerals to know
Some perspective on (geologic) time [w/ the Acasta gneiss!]
Due in large part to the lasting legacy of Christopher Columbus’s expeditions, North and South America will forever bear the mark of the “New World.” Whereas Europe has cathedrals centuries older than the United States itself, North America appears to not be able to offer much in terms of relics of antiquity. The earliest humans… Continue reading Some perspective on (geologic) time [w/ the Acasta gneiss!]
Emily Zawacki, Ph.D. 