Sedimentary, My Dear Watson

A 21-year-old geology (and Spanish and history) undergrad who loves rocks and wants other people to love them too! Here you'll find a diverse collection of all things geo and natural history related, targeted at varying levels of expertise.

*Please feel free to send in geo-related questions to the ASK page!*

Finally in Vancouver for GSA! I’ll be presenting Wednesday morning at 10:30 a.m. in the Holey Solar System session, some come to learn about Brussels Hill!

Finally in Vancouver for GSA! I’ll be presenting Wednesday morning at 10:30 a.m. in the Holey Solar System session, some come to learn about Brussels Hill!

themineralogist:

Copper, Aragonite and Malachite from Bolivia (by Xiao-dong Xu)

themineralogist:

Copper, Aragonite and Malachite from Bolivia (by Xiao-dong Xu)

How I feel getting ready for GSA

whatisgeology:

image

I’m putting together the final touches on my presentation right now! Hope to see a bunch of people there!

amnhnyc:

Happy #NationalFossilDay! Can you tell which of the above are dinosaur teeth? Below are the answers.
Clockwise from top:
Tyrannosaurus rex tooth (Late Cretaceous, western US) 
Tyrannosaur tooth (Late Cretaceous, Judith River, MT) 
Rugose coral (Middle Devonian, Falls of the Ohio, Clarksville, Indiana) 
Rugose coral (Paleozoic, locality unknown) 
Ornithomimid toe claw (Late Cretaceous, western US)
Rugose coral (Paleozoic, locality unknown)
Tyrannosaur tooth (Late Cretaceous, Judith River, MT) 
Rugose coral (Paleozoic, locality unknown)
Theropod tooth (Late Cretaceous, Ojo Alamo, NM) 
Tyrannosaur toe claw (Late Cretaceous, western US). 
All are fossils except, technically, the T. rex tooth at the top, which is actually a cast of a real tooth. The rugose corals (also known as solitary or horn corals) are very often mistaken for dinosaur teeth but are older than the oldest dinosaurs, having gone extinct around 250 million years ago (the oldest known dinosaurs are around 230 million years old).
Learn more on the Museum’s Division of Paleontology website. 

amnhnyc:

Happy #NationalFossilDay! Can you tell which of the above are dinosaur teeth? Below are the answers.

Clockwise from top:

  • Tyrannosaurus rex tooth (Late Cretaceous, western US)
  • Tyrannosaur tooth (Late Cretaceous, Judith River, MT)
  • Rugose coral (Middle Devonian, Falls of the Ohio, Clarksville, Indiana)
  • Rugose coral (Paleozoic, locality unknown)
  • Ornithomimid toe claw (Late Cretaceous, western US)
  • Rugose coral (Paleozoic, locality unknown)
  • Tyrannosaur tooth (Late Cretaceous, Judith River, MT)
  • Rugose coral (Paleozoic, locality unknown)
  • Theropod tooth (Late Cretaceous, Ojo Alamo, NM)
  • Tyrannosaur toe claw (Late Cretaceous, western US). 

All are fossils except, technically, the T. rex tooth at the top, which is actually a cast of a real tooth. The rugose corals (also known as solitary or horn corals) are very often mistaken for dinosaur teeth but are older than the oldest dinosaurs, having gone extinct around 250 million years ago (the oldest known dinosaurs are around 230 million years old).

Learn more on the Museum’s Division of Paleontology website

earthstory:

Sliced amethyst Not all crystals of a particular mineral are homogeneous, as revealed by this stunning slice across the long axis of an Indian amethyst, probably born in the Deccan flood basalts that were pouring out at the end of the Cretaceous and that may have played a part in the mass extinction at the end of the era. The crystal displays a complex growth history encompassing several generations of quartz, each precipitated from different fluids containing various amounts of iron and something that crystallised as dark matter, possibly the iron oxide mineral haematite in its steely grey form or particles of clay minerals.The first generation, shaped like a pale purple hourglass seems to be a twinned pair of crystals doped with small amounts of reduced Fe2+ (when amethyst is heated in an oxidising atmosphere it turns to citrine, coloured yellow by Fe3+) followed by an increase in the iron content (the darker purple outer layer. Next follows the opaque dark layer, and without scanning the piece under a microscope, I wouldn’t care to guess what it consists of.The next two layers have grown over these first generations in a more conventional hexagonal pattern, but with a complex deposition pattern that seems partly microcrystalline. They are separated by a layer very rich in iron, and both the red and grey hues of haematite are obvious. Inclusions of crystalline haematite fill these generations as well, visible as dark specks throughout the layers. LozImage credit: Rob Lavinsky/iRocks.com

earthstory:

Sliced amethyst 

Not all crystals of a particular mineral are homogeneous, as revealed by this stunning slice across the long axis of an Indian amethyst, probably born in the Deccan flood basalts that were pouring out at the end of the Cretaceous and that may have played a part in the mass extinction at the end of the era. The crystal displays a complex growth history encompassing several generations of quartz, each precipitated from different fluids containing various amounts of iron and something that crystallised as dark matter, possibly the iron oxide mineral haematite in its steely grey form or particles of clay minerals.

The first generation, shaped like a pale purple hourglass seems to be a twinned pair of crystals doped with small amounts of reduced Fe2+ (when amethyst is heated in an oxidising atmosphere it turns to citrine, coloured yellow by Fe3+) followed by an increase in the iron content (the darker purple outer layer. Next follows the opaque dark layer, and without scanning the piece under a microscope, I wouldn’t care to guess what it consists of.

The next two layers have grown over these first generations in a more conventional hexagonal pattern, but with a complex deposition pattern that seems partly microcrystalline. They are separated by a layer very rich in iron, and both the red and grey hues of haematite are obvious. Inclusions of crystalline haematite fill these generations as well, visible as dark specks throughout the layers. 

Loz

Image credit: Rob Lavinsky/iRocks.com

thought-cafe:

It’s here! Crash Course thecrashcourse Big History. John and Hank are in each intro scene, can you spot ‘em all?

Also, episode 1: The Big Bang. http://youtu.be/tq6be-CZJ3w

amnhnyc:

Corythosaurus is a member of the group of duck-billed dinosaurs called hadrosaurs, which walked and ran on their two hind legs. The species’ strange skull is capped by a crescent-shaped helmet that contains extended tubes, which formed elaborate nasal passages.

Collected in 1912 in Alberta, Canada, this Corythosaurus is among the finest dinosaur specimens ever found. The preservation of fossilized skin impressions and a meshwork of calcified tendons that stiffened the tall vertebrae make it a rare find.

This specimen is located in the Hall of Ornithischian Dinosaurs.

Hello! Can you recommend any Geology books for those with the most rudimentary knowledge of science? Science was always a struggle for me growing up, but geology is so fascinating to me. Thank you!
Anonymous

I highly recommend Reading the Rocks: The Autobiography of the Earth by Marcia Bjornerud. (Plus, I personally know the author, and she’s magnificent!) I definitely enjoy reading it as a geologist, but it’s perfectly geared to those who have more of a beginning knowledge of science; it’s typically categorized as ‘popular science,’ which basically just means that even if you’re not a geologist, you’ll still enjoy and understand it!

Another author I very highly recommend is Stephen Jay Gould. His writing is so vivid and easily accessible, it makes the natural work and natural history so fascinating! (He’s probably a large reason for why I fell in love with geology!) Bully for Brontosaurus and Wonderful Life: The Burgess Shale and the Nature of History are two fantastic books of his.

Anyone else have any great geology book recommendations to share?

Geology of the Indiana Dunes

Located in northwestern Indiana along the southern shore of Lake Michigan, the Indiana Dunes are a fantastic display of aeolian (wind) processes at work.

Incredibly tall sand dunes line the shores, and dune fields from former lake highstands extend even further back away.

These impressive ‘beach mountains’ originated from glacially transported sediment post-last glacial maximum [Pleistocene, ~18-14,000 yrs ago]. Glacial deposits are typically very poorly sorted but can become sorted by water (outwash), wave action, and wind action.

The dunes are primarily medium-grained quartz with finer-grained magnetite, so they are rather well sorted by specific weight. It would require wind ~15 mph to move this sized-sediment. 

Dunes typically have gentle upwind faces and steeper downwind faces [which is what generates the classic look of cross-bedding].
image

However, some dunes may become ‘blowouts,’ which is when a pristine dune has been modified, potentially by human activity/movement. Instead of having a linear or slightly concave down front face, the dune can become concave up in the direction of the wind and have a much steeper front slope.

However, the Indiana Dunes are being starved at sediment and now are at risk. As is evidenced by the large number of blowouts, the dunes are not healing themselves too well. Due to longshore drift,
image
t
he source of the sand for the dunes comes from the NE. As there is a large nuclear power plant along the shore toward the NE, the plant is likely blocking and prohibiting sand from traveling past it. Combined with this fact, negative feedbacks, human use, and other factors may be causing the starvation of these dunes.

All photos by author; graphics are linked to original sources

houroftherose:

Moss Agate is one of the most beautiful and interesting stones I know of. They often contain beautiful little scenes like this that look like hand-drawn landscapes or nature scenes. They are the result of various minerals and metals and the reaction that occurs when those minerals and metals interact.

houroftherose:

Moss Agate is one of the most beautiful and interesting stones I know of. They often contain beautiful little scenes like this that look like hand-drawn landscapes or nature scenes. They are the result of various minerals and metals and the reaction that occurs when those minerals and metals interact.