An unconformity is an erosional or non-depositional gap in the geologic record. They typically form when an older layer is subject to a period of erosion before the deposition of new sediments. This road cut near Payson, Arizona shows a pretty cool unconformity. Can you find where it is? Check the jump below to see… Continue reading Can you find the unconformity?
Even before I finished my first geology class, I (jokingly) told people that I was going to be a Spanish-speaking geologist at Disney World. While the rocks of Disney may not exactly be real, we can still learn about the geologic formations they take their inspiration from. Here’s a look at a few of the… Continue reading The Geology of Disneyland
Does it ever feel like geologists are speaking a different language? With so many different terms to describe and categorize rocks, learning the lexicon of a geologist can be a bit daunting. To help learn some basic geo lingo, here’s a (far from comprehensive) guide of some of the most important classification and terms geologists… Continue reading Geo Lingo | The Language of Geologists
While these dark gray spherical clasts could be mistaken for some type of fossil, they’re actually ooids, which are chemically precipitated sedimentary grains. Ooids form around a nucleus of a mineral grain or shell fragment. Concentric layers composed of calcium carbonate precipitate out and progressively coat the nucleus, forming a pattern almost like tree rings.… Continue reading Ooids • Sedimentary Spheres
This piece of glaciated breccia from the Brussels Hill meteorite impact structure in Brussels, Wisconsin is probably one of my favorites in my collection. It’s not the oldest, nor is it necessarily the prettiest, but it holds one of the best stories. This rock began its life ~440 million years ago during the Silurian Period.… Continue reading Glaciated breccia: A three-part rock story
Have you ever wondered, “How do geologists know how old a rock is?” Geochronology is the science of determining how old rocks, sediments and fossils are. Whether they formed 4 billion years ago or within the historic record, geologists can employ geochronologic methods to determine either the relative or absolute ages of these materials. Radiometric dating–which measures… Continue reading Introduction to Geochronology
Typically when we think of rocks, we don’t often picture them as having vibrant hues. Minerals themselves often come in a spectacular array of colors, but rocks overall tend to have more muted tones and earthy colors. These rocks (pictured above) from the Buckskin Mountains in western Arizona stand out in stark contrast to the… Continue reading How do you make a green rock?
If you’re a structural geologist or geology student in the midcontinent region, you’ve most likely made the pilgrimage to Van Hise Rock. Located near Rock Springs, Wis., in the Baraboo quartzite range, Van Hise Rock is among the best-known structural geology landmarks in the Midwest. Van Hise Rock provides spectacular exposure of the nearly vertical… Continue reading Van Hise Rock
Folded quartzite and phyllite, with axial planar cleavage in the phyllite South limb of the Baraboo (Wis.) syncline Image by author
I made some slices of one of the breccias from my research site, and look at how pretty they look! [Breccias are rocks composed of broken fragments of other rocks or minerals, all cemented together in a fine-grained matrix]