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vesicles
Elongate vesicles in basalt from the Bonito Lava Flow, west of Sunset Crater, AZ. Gas bubbles trapped in the lava originated these cavities, with the stretching related to a preferential direction of flow. This example of volcanic activity is about 1,000 years old, and is part of a larger Volcanic Field (San Francisco Volcanic Zone, AZ, USA).
Coryphodon
Pantodonts are an extinct type of large mammals, somehow reminiscent of hippos. Skull (from Paleocene of Colorado, US) on display at the Field Museum of Natural History, Chicago.
Trail11SteamboatRock
Entrenched meander, Steamboat Rock at Harpers Corner, Dinosaur N.M.
Recumbent anticline
Anticlinal folding in Pennsylvanian strata of the Belden Fm. (Sweetwater Creek, near Dotsero, CO). Monoclinal to recumbent folds (similar to this one) can be caused by displacement connected with the termination of a thrust fault buried at depth. Some have interpreted this particular fold in this way, linking it with thrust activity during the Laramide orogeny. Note that the lithology of the Belden Fm., which consists of bedded shales, limestone, and evaporites, favors ductile deformation. Layers that tend to resist plastic deformation under stress are termed "competent," and a contrast between competent (e.g., sandstone, chert) and less competent (e.g., shale, gypsum) beds can produce spectacular folding.
Eocene prawn and herring
What do these two fossils share? They died together, they are spectacularly preserved, and they were buried rapidly. These specimens of a prawn (Bechleja rostrata) and a herring (Knightia eocaena) are from Eocene deposits of the Fossil Lake, Wyoming, on display at the Chicago Field Museum of Nature and History.
Glenwood_Cny
WATER: Dissolution caves in the Mississippian Leadville limestone, Glenwood Canyon, Interstate-70 --- As acidic water dissolved the limestone, caves formed as seen here and sinkholes formed at the upper surface. In the standard interpretation, the ancient sinkhole land surface at the top of this formation formed a karst topography similar to what is seen in some places in Florida today.
Psylophyton forbesii
Trimerophytes were leafless vascular plants, with branches departing from the stem in a spiral pattern. This specimen containing multiple stems (several cm in size) is from the Devonian of Quebec, on display at the Field Museum of Natural History, Chicago.
Rt139 MesaVerdeFm
Honeycomb weathering, Mesa Verde Fm, Rt.139 north of Grand Junction --- Freezing and thawing of wet sandstone cliffs loosens the sand grains that are then blown away by the wind.
Araripescorpius ligabuei
The body plan of fossil scorpions is not much different from modern ones: an example of morphological stasis. This is a Cretaceous example from the Crato Formation of Brazil. Specimen on display at the Paleontological Museum in Santana do Cariri, few cm in size.