 Erosion forms of limestone in a rock shelter at Rough Trail. Red River Gorge, Kentucky, November 6, 1999.
 Tree roots and erosion forms on a limestone rock at Rough Trail. Red River Gorge, Kentucky, November 6, 1999.
 Erosion of a limestone rock at Rough Trail. Red River Gorge, Kentucky, November 6, 1999.
 Limestone erosion forms at Koomer Ridge Trail. Red River Gorge, Kentucky, November 7, 1999.
 Mushroom-like limestone erosion forms at Koomer Ridge Trail. Red River Gorge, Kentucky, November 7, 1999.
 Erosion of limestone near Gray s Arch. Red River Gorge, Kentucky, November 6, 1999.
 Limestone rocks, view from Sheltowee Trail near Chimney Top Rock. Red River Gorge, Kentucky, November 6, 1999.
 A.S. on Rough Trail. Red River Gorge, Kentucky, November 6, 1999.
 View from Rough Trail. Red River Gorge, Kentucky, November 6, 1999.
 Rough Trail to Gray s Arch. Red River Gorge, Kentucky, November 5, 1999.
 A small maple on Rough Trail. Red River Gorge, Kentucky, November 6, 1999.
 Rough Trail to Gray s Arch. Red River Gorge, Kentucky, November 5, 1999.
 Pine forest on Rough Trail. Red River Gorge, Kentucky, November 6, 1999.
 A tree with very big leaves on Rough Trail. Red River Gorge, Kentucky, November 6, 1999.
 Rhododendron in a canyon, view from Rough Trail. Red River Gorge, Kentucky, November 6, 1999.
 Multicolor maple leaves on Rough Trail. Red River Gorge, Kentucky, November 6, 1999.
 Unknown dwarf berries on Rough Trail. Red River Gorge, Kentucky, November 6, 1999.
 Blueberry and rhododendron bushes on Rough Trail. Red River Gorge, Kentucky, November 6, 1999.
 Sheltowee Trail near Chimney Top Rock. Red River Gorge, Kentucky, November 6, 1999.
 A fungus (?) on a birch, Sheltowee Trail near Chimney Top Rock. Red River Gorge, Kentucky, November 6, 1999.
 View of canyon walls at evening from Sheltowee Trail near Chimney Top Rock. Red River Gorge, Kentucky, November 6, 1999.
 View of rock shelters from the top of Gray s Arch. Red River Gorge, Kentucky, November 6, 1999.
 Gray s Arch, view from rock shelters. Red River Gorge, Kentucky, November 6, 1999.
 Gray s Arch, view from rock shelters. Red River Gorge, Kentucky, November 6, 1999.
 A.S. on Buck Trail. Red River Gorge, Kentucky, November 7, 1999.
 Buck Trail. Red River Gorge, Kentucky, November 7, 1999.
 Sheltowee Trail. Red River Gorge, Kentucky, November 6, 1999.
 Forest near Buck Trail. Red River Gorge, Kentucky, November 7, 1999.
 View from Pinch Em Tight Trail. Red River Gorge, Kentucky, November 7, 1999.
 View from Pinch Em Tight Trail. Red River Gorge, Kentucky, November 7, 1999.
 Mushrooms in moss at Buck Trail. Red River Gorge, Kentucky, November 7, 1999.
 Flowers on a stone at Buck Trail. Red River Gorge, Kentucky, November 7, 1999.
 Oak forest near Pinch Em Tight Trail. Red River Gorge, Kentucky, November 7, 1999.
 View from Pinch Em Tight Trail. Red River Gorge, Kentucky, November 7, 1999.
 View from Pinch Em Tight Trail. Red River Gorge, Kentucky, November 7, 1999.
 Bottom of a canyon, view from Sheltowee Trail. Red River Gorge, Kentucky, November 6, 1999.
 View of a canyon from Pinch Em Tight Trail. Red River Gorge, Kentucky, November 7, 1999.
 Bamboo brushes on the bottom of a canyon near Sheltowee Trail. Red River Gorge, Kentucky, November 6, 1999.
 Creeping fern among dry leaves and needles on Koomer Ridge Trail. Red River Gorge, Kentucky, November 7, 1999.
 Forest below Gray s Arch. Red River Gorge, Kentucky, November 6, 1999.
 Rhododendron, fir and maples near Gray s Arch. Red River Gorge, Kentucky, November 6, 1999.
 Forest near Gray s Arch at morning. Red River Gorge, Kentucky, November 6, 1999.
 View from the top of Gray s Arch at morning. Red River Gorge, Kentucky, November 6, 1999.
 Forest near Gray s Arch at morning. Red River Gorge, Kentucky, November 6, 1999.
 Forest near Gray s Arch at morning. Red River Gorge, Kentucky, November 6, 1999.
 Forest near Gray s Arch at morning. Red River Gorge, Kentucky, November 6, 1999.
 View from the top of Gray s Arch at morning. Red River Gorge, Kentucky, November 6, 1999.
 Gray s Arch with rhododendron on foreground. Red River Gorge, Kentucky, November 6, 1999.
 Tobacco farm near Slade, Kentucky, November 5, 1999.
 Erosion of the dome of Enchanted Rock, view from Freshman Mountain. Enchanted Rock State Natural Area, Fredericksburg, Texas, December 25, 2018
 View of limestone erosion from a trail along a western slope of Mount Yoash, 4 miles north-west from Eilat. The Middle East, January 17, 2002
 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
 Some dark-green crustose lichen on a limestone rock near the river in Pedernales Falls State Park. Johnson City, Texas, January 11, 2019
 Limestone erosion in Harrarah (Al Kharrarah). Southern Qatar, March 27, 2015
 Erosion of limestone rocks in Harrarah (Al Kharrarah). Southern Qatar, March 27, 2015
 Erosion of soft limestone in Harrarah (Al Kharrarah). Southern Qatar, March 27, 2015
 Erosion of limestone slabs in Harrarah (Al Kharrarah). Southern Qatar, March 27, 2015
 Bordered scale lichen (Psora pseudorussellii) on a limestone conglomerate rock near the river in Pedernales Falls State Park. Johnson City, Texas, January 11, 2019
 Erosion of beach limestone in Purple Island (Jazirat Bin Ghanim). Al Khor, Qatar, February 14, 2015
 Erosion of limestone cliffs in Maszhabiya (Al Mashabiya) Reserve near Abu Samra. Southern Qatar, April 1, 2016
 Erosion of limestone near Salwa Road in area of Rawdat Ekdaim. Southern Qatar, April 11, 2015
 Wind erosion of limestone cliffs in Maszhabiya (Al Mashabiya) Reserve near Abu Samra. Southern Qatar, May 20, 2016
 View of Wabash River from a trail to Fort Ouiatenon. Indiana, November 13, 1999
 Erosion of an orange limestone formation in Maszhabiya (Al Mashabiya) Reserve near Abu Samra. Southern Qatar, April 1, 2016
 Wind erosion of limestone cliffs in Maszhabiya (Al Mashabiya) Reserve near Abu Samra. Southern Qatar, June 25, 2016
 Erosion of the edge of limestone cliffs in Maszhabiya (Al Mashabiya) Reserve near Abu Samra. Southern Qatar, April 1, 2016
 Limestone wind erosion on the tabletop hill in Maszhabiya (Al Mashabiya) Reserve near Abu Samra. Southern Qatar, April 29, 2016
 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 a mossy limestone rock in Pedernales Falls State Park. Johnson City, Texas, January 11, 2019
 Soil erosion in Happy Hollow Park. West Lafayette, Indiana, October 27, 1999.
 Erosion of a limestone formation on a plateau of a tabletop mountain in Maszhabiya (Al Mashabiya) Reserve near Abu Samra. Southern Qatar, April 1, 2016
 Erosion of a rock formation on a tabletop hill in Maszhabiya (Al Mashabiya) Reserve near Abu Samra. Southern Qatar, April 8, 2016
 Early snowfall on Rock Street near Museum of Fall River Historical Society in historic Highlands District. Fall River, Massachusetts, November 13, 2004
 Rough weathered limestone rocks in Harrarah (Al Kharrarah). Southern Qatar, March 27, 2015
 Rough eroded limestone rocks in Harrarah (Al Kharrarah). Southern Qatar, March 27, 2015
 Limestone with fossils near Whiskey Bridge of Brazos River, on Highway 21 west from Bryan. Texas, November 29, 2019
 Picnic shelter in Hensel Park. College Station, Texas, November 26, 2017
 Rock Street in historic Highlands District. Fall River, Massachusetts, November 13, 2004
 A rock in the middle of Bell Rock Road in Freetown - Fall River State Forest. Massachusetts, August 24, 2003
 Potholes Park, Fall Creek Gorge. The trip was organized by Purdue University International Center. Near Pine Village, Indiana, June 5, 1999.
 A dam in Russells Mills village, on Paskamansett River, view from Rock O Dundee Road. Dartmouth, Massachusetts, November 28, 2003
 A dam in Russells Mills village, on Paskamansett/Slocums River, view from Rock O Dundee Road. Dartmouth, Massachusetts, November 23, 2003
 A dam in Russells Mills village, on Paskamansett/Slocums River, view from Rock O Dundee Road. Dartmouth, Massachusetts, November 25, 2004
 A dam in Russells Mills village, on Paskamansett/Slocums River, view from Rock O Dundee Road. Dartmouth, Massachusetts, November 28, 2003
 A dam in Russells Mills village, on Paskamansett/Slocums River, view from Rock O Dundee Road. Dartmouth, Massachusetts, November 13, 2003
 Rock foam lichen (Stereocaulon saxatile)(?) on a rough surface of a granite stone in Kannelyarvi, 45 miles north from Saint Petersburg. Russia, May 25, 2019
 Overcoming a tub in a creek in Potholes Park (Fall Creek Gorge) by an international student of Purdue University. Near Pine Village, Indiana, June 5, 1999.
 Inspecting a creek in Potholes Park (Fall Creek Gorge) by international students of Purdue University. Near Pine Village, Indiana, June 5, 1999.
 Forest of Enfield gorge, from Rim Trail, in Robert H. Treman State Park. Ithaca, New York, November 2, 2005
 International students of Purdue University walking over rapids and tubs of a creek in Potholes Park (Fall Creek Gorge) near Pine Village. Indiana, June 5, 1999.
 Fallen sycamore tree in snow near Gorge Trail in Taughannock Falls State Park. New York, November 23, 2005
 Fossilized oyster sea shells Ostrea latimarginata(?) in a limestone layer (Dukhan Limestone Member) of Dammam Formation in Jaow Al Hamar depression south from Trainah. Southern Qatar, November 6, 2015
 View in direction to Rough Point from Cliff Walk at Sheep Point, behind Gull Rock tunnel. Newport, Rhode Island, February 5, 2004.
 Fall colors of Enfield gorge, view from Rim Trail, in Robert H. Treman State Park. Ithaca, New York, November 2, 2005
 Limestone rock formation in Maszhabiya (Al Mashabiya) Reserve near Abu Samra. Southern Qatar, April 1, 2016
 Limestone rock layers in Maszhabiya (Al Mashabiya) Reserve near Abu Samra. Southern Qatar, April 1, 2016
 Entrance to Nahal Tseelim River Gorge, 2 miles north from Masada. The Middle East, January 20, 2001
 Fall colors of Enfield gorge, zoomed, view from Rim Trail, in Robert H. Treman State Park. Ithaca, New York, November 2, 2005
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