Mi(ni)Geo

Nivel estromatolítico (by Imrishale)

Un pequeño nivel estromatolítico situado entre restos carbonatados.

The hard drought in Texas this summer has taken its toll; crops are shriveled, rivers are drying up and even cacti are showing stress. But droughts such as this offer a rare glimpse of an extensive collection of dinosaur tracks at the Dinosaur Valley State Park near Glen Rose, Texas. Normally covered in water, the tracks of sauropods and theropods are for the time being exposed in the limestone bed of the Paluxy River. This small sauropod print is approximately 12 in (30 cm) across. The setting for this park was formed by sediment deposited more than 100 million years ago along rivers that once flowed into an ancient sea. Over perhaps the last 1 million years, the layered sediment has been gradually worn away revealing the long ago submerged footprints. Photo taken on August 2, 2011. Credit: Loren Ann Stiles. (via EPOD)

Travertine ridge view (by Ale*)

This hot spring has built over time beautiful travertine ridges in this area of Eastern California. In this case, travertine formed when hot water supersaturated in calcium carbonate reached the surface. Loss of carbon dioxide to the atmosphere causes calcite precipitation and here are the ridges. The area around the ridges looks desolate and stark because of the high temperature of underground water (65°C / 150°F at the spring proper, less than that - of course - where people go to soak in artificial pools built over time). In the background, the verdant Sierra Nevada rises as a steep wall to the west.

Bridgeport, Mono County, California

The Glamorgan Heritage Coast of South Wales, U.K., formed millions of years ago when present day Wales was nearly completely submerged. These exposed, eroded early Lower Lias or early Jurassic rocks, primarily limestone and shale, are readily accessible to rock hounds and to people who simply enjoy strolling along the shore. The beach platforms, cliffs and sea caves (like this one) here are all quite spectacular both when viewed from the cliff-top paths and when exploring up close. Make sure to consult tidal charts before investigating the sea caves since this portion of the Welsh coast has a considerable tidal range - over 50 ft (16 m). Photo taken on July 20, 2011. Credit: Stephen Gledhill. (via EPOD)

inlovewithgeosciences:

Karst landscape geology

“Cutaway artwork showing the features of a karst limestone landscape formed by erosion. The limestone rock has been shaped by natural chemical erosion. Carbon dioxide in the air dissolves in rainwater to form carbonic acid. This acid erodes the limestone rock as the water flows over it. At far right, a river flows down into the ground to form an underground river (across bottom), emerging at lower left. Two layers of caves are shown, with water seeping down from above to form stalactites, stalagmites, which can join to form large pillars. At left, the rock has been exposed, forming a limestone pavement.”

(via it-sfullofstars)

Aven Armand cave, Lozère, France (by F.Alabart)

Deformed ooids. (via Ben van der Pluijm)

Äigu Beds of the Kaugatuma Formation exposed on the northwestern shore of the Sõrve Peninsula on Saaremaa. These are Late Silurian (Pridoli) limestones with a great abundance of crinoid fragments — so many that they are locally called “ringstones”. The image shows a crinoid stem and isolated ring-like columnals. (via Wooster Geologists)

El Cerro del Hierro, en la Sierra Norte sevillana, se encuentra entre los términos municipales de San Nicolás del Puerto y Constantina. Se trata de un paleokarst que ha quedado expuesto tras la explotación de las limonitas y demás óxidos de hierro presentes entre las calizas. Foto: Gonzalo García, 2004. (via MTI Blog)