Jack Dykinga / Tent rocks in the Peralta Canyon, New Mexico, USA. Rocks are conical formations of eroded volcanic tuff and pumice supporting 'cap rocks'.

Jack Dykinga / Sunlit cliffs of Closed Canyon reflected in a seasonal rainwater pool in Santana tuff rock formation, Big Bend Ranch State Park, Texas, USA

Jack Dykinga / Engelmann spruce (Picea engelmannii) growing amongst pinnacles of volcanic tuff, dawn, Wheeler Geological Area Wilderness, Rio Grande National Forest, Colorado, USA

Jack Dykinga / Tufa pinnacles in the sunset afterglow at the edge of Mono Lake, Mono Lake State Reserve, California, USA

Espen Bergersen / Hverfjall is a tephra cone or tuff ring volcano in northern Iceland, to the east of Myvatn, Iceland. May 2016

Espen Bergersen / Hverfjall a tephra cone or tuff ring volcano, northern Iceland. May 2016.

Espen Bergersen / Hverfjall is a tephra cone or tuff ring volcano in northern Iceland, to the east of Myvatn, Iceland. May 2016

Espen Bergersen / People walking along the rim of Hverfjall. Hverfjall is a tephra cone or tuff ring volcano in northern Iceland, to the east of Myvatn. Iceland, May 2016

Tui De Roy / Olivine beach formed from crystals leached out of eroded tuff cone, Whale Bay, Santa Cruz Island, Galapagos Islands.

Tui De Roy / Pinnacle Rock, remnant of old eroded tuff cone, Bartolome Island. Galapagos Islands, June 2011.

John Cancalosi / Welded Tuff (a rock formed from consolidated volcanic rock) Mexico

Tui De Roy / Eroded volcanic tuff cones with Galapagos sea lion (Zalophus wollebaeki) sleeping on sandy beach, Punta Pitt, San Cristobal Island, Galapagos Islands, Ecuador. May 2012.

Tui De Roy / Eroded volcanic tuff cones with Galapagos sea lions (Zalophus wollebaeki) sleeping on sandy beach, Punta Pitt, San Cristobal Island, Galapagos Islands, Ecuador. May 2012.

Tui De Roy / Eroded volcanic tuff cones, with Sesuvium vegetation, Punta Pitt, San Cristobal Island, Galapagos Islands, Ecuador. May 2012.

Tui De Roy / Sally lightfoot crabs (Grapsus grapsus) on basaltic lava shore, with coral beach and old eroded tuff cone. Cerro Brujo, San Cristobal, Galapagos Islands, Ecuador. May 2012.

Tui De Roy / Pinnacle Rock, iconic Galapagos Landmark formed of eroded tuff stone, Bartolome Island, Galapagos, Ecuador. June 2011.

Tui De Roy / Volcanic caldera with tuff cone and lake, formed by collapse of shield volcano. Cerro Azul, Isabela Island, Galapagos, Ecuador.

Tui De Roy / Tuff Cone Crater, Bainbridge Rocks, Santiago Island, Galapagos, Ecuador.

Doug Perrine / Male Hawaiian monk seal (Monachus schauinslandi) (with what appears to be massive shark bite scar across abdomen) ) at Vertical Awareness dive site, an underwater pinnacle of volcanic tuff at Lehua Ro...

Doug Perrine / Male Hawaiian monk seal (Monachus schauinslandi) (with what appears to be massive shark bite scar across abdomen) ) at Vertical Awareness dive site, an underwater pinnacle of volcanic tuff at Lehua Ro...

Bryan and Cherry Alexander / Dive boat by Pinnacle Rock, the eroded remains of a tuff cone, by the the volcano on Isla Bartolome. Galapagos, January 2005.

Bryan and Cherry Alexander / Pinnacle Rock, the eroded remains of a tuff cone, by the the volcano on Isla Bartolome. Santiago, Galapagos, January 2005.

Fabio Liverani / Sassi, houses dug into the tuff rock, Matera at night, Basilicata, Southern Italy, June 2009

Fabio Liverani / Two people walking down steps, Sassi, houses dug into the tuff rock, Matera, Basilicata, Southern Italy, June 2009

Fabio Liverani / Old abandoned Sassi, houses dug into the tuff rock, Matera, Basilicata, Southern Italy, June 2009

Fabio Liverani / Sassi, houses dug into the soft tuff rock, Matera, Basilicata, Southern Italy, June 2009

Fabio Liverani / Sassi, houses dug into the tuff rock, Matera, Basilicata, Southern Italy, June 2009

Fabio Liverani / Sassi, houses dug into the tuff rock, Matera, Basilicata, Southern Italy, June 2009

Fabio Liverani / Sassi, houses dug into the tuff rock, Matera, Basilicata, Southern Italy, June 2009

Pete Oxford / Pinnacle rock - an eroded tuff cone on Bartolome Is, Galapagos 2006

Pete Oxford / Kicker Rock / León Dormido said to resemble a sleeping lion. It is an eroded tuff cone whose sheer-sided cliffs are frequented by seabirds eg boobies, frigates and tropic birds.

Luciano Candisani / Tuff arch just offshore Darwin Island, Galapagos Islands, Ecuador

Pete Oxford / Tuff rock reflected in the sea off Tagus Cove, Isabela Island, Galapagos

Pete Oxford / Kicker Rock or Leon Dormido is an eroded tuff cone whose sheer sided cliffs are frequented by Boobies, Frigatebirds and tropic birds, Galapagos Islands, Ecuador

Pete Oxford / Eroded Tuff cone, Punta Pitt, San Cristobel Island, Galapagos Islands

Jack Dykinga / Saguaro {Carnegia gigantea}, Paloverde {Cercidium microphyllum} and Mesquite {Prosopis glandulosa} on cliffs of volcanic tuff, Hot Springs Canyon, Arizona, USA

Mark Taylor / Eroded volcanic tuff, Kapadokia, Turkey.

Pete Oxford / Eroded tuff cone, Atlosova Island, Kuril Islands, Eastern Russia, Pacific Ocean

Tim Fitzharris / Shiprock, the basalt core of an extinct volcano, tuff-breccia ejected boulders in foreground, New Mexico

Tim Fitzharris / Shiprock, the basalt core of an extinct volcano, tuff-breccia ejected boulders in foreground, New Mexico

Tui De Roy / Volcanic tuff formations on high Andean plateau, Mismi Mountain, Colca Canyon, Peru

Tui De Roy / Old tuff cone formation deeply eroded by rain and time, some of the oldest terrain in the islands, Punta Pitt, San Cristobal Island, Galapagos Islands, Ecuador

Tui De Roy / Sailboat dwarfed by Kicker Rock, an old eroded tuff cone, San Cristobal Island, Galapagos Islands, Ecuador

Tui De Roy / Kicker Rock, old eroded tuff cone, San Cristobal Island, Galapagos Islands, Ecuador

Tui De Roy / View of Bartolome Island, near Santiago Island, showing numerous volcanic spatter and tuff cones of varying ages. Galapagos Islands, Ecuador.

Tui De Roy / Kicker Rock, Leon Dormido, tuff formation, at sunset, San Cristobal Island, Galapagos Islands, Ecuador.

Tui De Roy / Saline lake in volcanic tuff cone crater, Tagus Cove, Isabela Island, Galapagos, South America. June, 2021.

Tui De Roy / Tuff cone, Floreana Island, Galapagos, South America. August, 2019.

Tui De Roy / Saline lake in volcanic tuff cone crater, Bainbridge Islets, Galapagos, South America. October, 2020.

Tui De Roy / Tuff cone at sunset, Bainbridge Islets, Galapagos, South America. October, 2020.

Tui De Roy / Saline lake in volcanic tuff cone crater, with rainbow, Bainbridge Islets, Galapagos, South America. October, 2020.

Tui De Roy / Bartolome Pinnacle Rock, remains of eroded tuff cone, Galapagos, South America. August, 2019.

Tui De Roy / Brown noddies (Anous stolidus) perching on volcanic tuff, erosion showing layering of volcanic ash, Isabela Island, Galapagos, South America.