Scaly stippled lichen (Endocarpon pusillum) on a thin layer of soil over exposed limestone rocks overgrown by prickly pears near a former pond in Washington-on-the-Brazos State Historic Site. Washington, Texas, December 28, 2019
Close-up of scaly stippled lichen (Endocarpon pusillum) on a thin layer of soil over exposed limestone rocks overgrown by prickly pears near a former pond in Washington-on-the-Brazos State Historic Site. Washington, Texas, January 18, 2020
Limestone cliffs rocks of rocky ridge of Jebel Fuwairit. Northern Qatar, December 12, 2014
Bordered scale lichen (Psora pseudorussellii) on a limestone conglomerate rock near the river in Pedernales Falls State Park. Johnson City, Texas, January 11, 2019
Overhanging limestone rocks in Maszhabiya (Al Mashabiya) Reserve near Abu Samra. Southern Qatar, June 25, 2016
Sunrise over limestone rocks in Maszhabiya (Al Mashabiya) Reserve near Abu Samra. Southern Qatar, June 25, 2016
Bush of Haloxylon salicornicum (Hammada elegance) on limestone rocks in Maszhabiya (Al Mashabiya) Reserve near Abu Samra. Southern Qatar, June 25, 2016
Prickly pears (Opuntia) on exposed limestone rocks near a former pond in Washington-on-the-Brazos State Historic Site. Washington, Texas, January 18, 2020
Broken limestone rocks in Harrarah (Al Kharrarah). Southern Qatar, March 27, 2015
Weathered limestone rocks in Harrarah (Al Kharrarah). Southern Qatar, March 27, 2015
White patch of Aspicilia lichen on a limestone rock in Pedernales Falls State Park. Johnson City, Texas, January 11, 2019
Erosion forms of limestone on a rock shelter at Rough Trail. Red River Gorge, Kentucky, November 6, 1999.
Limestone rocks in a desert on roadside of a road to Sawda Natheel. Southern Qatar, February 5, 2016
Rough eroded limestone rocks in Harrarah (Al Kharrarah). Southern Qatar, March 27, 2015
Limestone rock layers in Maszhabiya (Al Mashabiya) Reserve near Abu Samra. Southern Qatar, April 1, 2016
Erosion forms of limestone in a rock shelter at Rough Trail. Red River Gorge, Kentucky, November 6, 1999.
Aerodynamically eroded limestone rocks (wind abrasion) on a tabletop mountain in Maszhabiya (Al Mashabiya) Reserve near Abu Samra. Southern Qatar, June 25, 2016
Aeolian abrasion of limestone rocks (carved by drifting sand) south from Abu Nahlah. Qatar, April 25, 2014
Erosion of a limestone rock at Rough Trail. Red River Gorge, Kentucky, November 6, 1999.
Limestone rocks, view from Sheltowee Trail near Chimney Top Rock. Red River Gorge, Kentucky, November 6, 1999.
Fossil shark tooth (Galeocerdo(?)) embedded in a rock of Dammam Formation (Lower Dam limestones) in a site on flanks of Rawdat Al Heshaimiya(?) depression south from Trainah. Southern Qatar, November 6, 2015
Limestone rocks on a beach in Abu Samra, near Salwa Road. Qatar, October 16, 2015
Mushroom shaped limestone rock in area of Jebel Al-Nakhsh (Khashm an Nakhsh) in south-western Qatar, March 11, 2016
Tree roots and erosion forms on a limestone rock at Rough Trail. Red River Gorge, Kentucky, November 6, 1999.
Aeolian abrasion of limestone rocks (carved by drifting sand) in Traina Sinkhole (karst depression) AOI 2 north-west of Khor Al Adaid. Southern Qatar, January 23, 2015
Aeolian abrasion of limestone rocks (carved by drifting sand) at the foot of a sand dune near Harrarah, west from Mesayeed, south-west from Doha. Qatar, March 19, 2013
Weathered limestone rocks in area of Nakhsh Mountain near Salwa Road in southern Qatar, May 8, 2015
Effects of wind abrasion on limestone rocks near Harrarah, west from Mesayeed, south-west from Doha. Qatar, March 19, 2013
Crustose lichen Caloplaca aurantia with orange-brown apothecia crowded in the center of the thallus on a limestone rock in desert near industrial zone of Ras Laffan, north from Doha. Qatar, March 23, 2013
Limestone rocks in Harrarah (Al Kharrarah). Southern Qatar, March 27, 2015
Erosion of limestone rocks in Harrarah (Al Kharrarah). Southern Qatar, March 27, 2015
Rough weathered limestone rocks in Harrarah (Al Kharrarah). Southern Qatar, March 27, 2015
Limestone rock formation in Maszhabiya (Al Mashabiya) Reserve near Abu Samra. Southern Qatar, April 1, 2016
Tetraena qatarense (Zygophyllum qatarense) plant on a surface of limestone rock in Harrarah (Al Kharrarah). Southern Qatar, April 23, 2016
Cracked limestone rocks in Maszhabiya (Al Mashabiya) Reserve near Abu Samra. Southern Qatar, June 25, 2016
Bush of Salsola cyclophylla on limestone rocks in Maszhabiya (Al Mashabiya) Reserve near Abu Samra. Southern Qatar, June 25, 2016
Bush of Traganum nudatum on limestone rocks in Maszhabiya (Al Mashabiya) Reserve near Abu Samra. Southern Qatar, June 25, 2016
Limestone rocks near the falls in Pedernales Falls State Park. Johnson City, Texas, January 11, 2019
Smooth limestone rocks near the water stream in Pedernales Falls State Park. Johnson City, Texas, January 11, 2019
Black limestone rocks in Pedernales Falls State Park. Johnson City, Texas, January 11, 2019
Some whitish lichen on a limestone rock near the river in Pedernales Falls State Park. Johnson City, Texas, January 11, 2019
Button lichen (Buellia) on limestone rock near the river in Pedernales Falls State Park. Johnson City, Texas, January 11, 2019
Button lichen (Buellia) on a limestone rock in Pedernales Falls State Park. Johnson City, Texas, January 11, 2019
Patches of button lichen (Buellia) on a limestone rock in Pedernales Falls State Park. Johnson City, Texas, January 11, 2019
Some dark-green crustose lichen on a limestone rock near the river in Pedernales Falls State Park. Johnson City, Texas, January 11, 2019
Ruffle lichen (Parmotrema) on a mossy limestone rock in a red cedar forest in Pedernales Falls State Park. Johnson City, Texas, January 11, 2019
Ruffle lichen (Parmotrema) on a mossy limestone rock in Pedernales Falls State Park. Johnson City, Texas, January 11, 2019
Ruffle lichen (Parmotrema) in shade on a mossy limestone rock in Pedernales Falls State Park. Johnson City, Texas, January 11, 2019
Rock shield lichen (Xanthoparmelia) on a mossy limestone rock in Pedernales Falls State Park. Johnson City, Texas, January 11, 2019
Button lichen (Buellia) on a limestone rock in Pedernales Falls State Park. Johnson City, Texas, January 11, 2019
Buellia and other lichens on a limestone rock in Pedernales Falls State Park. Johnson City, Texas, January 11, 2019
Button lichen (Buellia) on a mossy limestone rock in Pedernales Falls State Park. Johnson City, Texas, January 11, 2019
Rock shield lichen (Xanthoparmelia)(?) on a limestone rock in a forest in Pedernales Falls State Park. Johnson City, Texas, January 11, 2019
Rock shield lichen (Xanthoparmelia) on limestone in a red cedar forest in Pedernales Falls State Park. Johnson City, Texas, January 11, 2019
Turbin lichen (Cladonia peziziformis) on side surface of sandstone or limestone rocks near the ground at Lake Somerville Trailway near Birch Creek Unit of Somerville Lake State Park. Texas, January 25, 2019
Rock lettuce (Pinaropappus roseus) near a piece of limestone near a driveway of an apartment on George Bush Drive. College Station, Texas, March 26, 2019
Dark crust of scaly stippled lichen (Endocarpon pusillum) on a thin layer of soil over exposed limestone rocks overgrown by prickly pears in Washington-on-the-Brazos State Historic Site. Washington, Texas, December 28, 2019
Scaly stippled lichen (Endocarpon pusillum) on a thin layer of soil over exposed limestone rocks overgrown by prickly pears near a former pond in Washington-on-the-Brazos State Historic Site. Washington, Texas, January 18, 2020
Devil s Bridge (Chertov Most), also known as the Cascade, located near the Upper Ponds in Catherine Park. It is constructed from rough-hewn limestone and granite blocks (tufa) to resemble a natural rock formation or an ancient grotto. The "bridge" actually functions as a decorative cascade or dam between the ponds. Pushkin (former Tsarskoe Selo) near Saint Petersburg, Russia, October 10, 2025
