Trilobite fragment (probably Ollenoides serratus), Walcott Quarry member of the Burgess Shale, British Columbia

Rotated tension gash in the contact aureole of the Inyo Batholith, White-Inyo Mountains, California

Intrusive breccia in the mixing zone of the 149 Ma Guadalupe Igneous Complex, Sierra Nevada, California

Ball-and-pillow features alongside flame structure in the mixing zone of the Guadalupe Igneous Complex, Sierra Nevada

Boudinage in mylonite shear zone near the base of the Guadalupe Igneous Complex, Sierra Nevada

Ladder dike in the Half Dome Granodiorite, Yosemite —

Detail of ladder dike in the Half Dome Granodiorite, Yosemite

Nearly circular mafic enclave in the Half Dome Granodiorite, Yosemite

Glacially-carved granite domes near Tenaya Lake, Yosemite

Tufa, Mono Lake, California

Intricate fluting and spatter on the wall of a lava tube, Raufarhólshellir, Iceland

Ice stalgmites in Raufarhólshellir lava tube, Iceland

Intrusive breccia at Island Lake, Sierra Nevada

Large orthoclase crystals in pegmatite near Island Lake, Sierra Nevada. Camera filter is 4 cm for scale.

Glacially-polished columnar jointing, Devil’s Postpile, California

Meter-scale columnar jointing in the main flow of the Bishop Tuff, Owens Valley, California

Airfall ash and pumice from the Bishop Tuff, Owens Valley, California

Students climb one of the tallest sand dunes in North America - Eureka Dunes, Death Valley

Colorful stratigraphy of the Kingston Peak Formation, Beck Canyon, California

Meter-wide magnetite veins cutting the Beck Springs Dolomite, Beck Canyon, California

Detail of magnetite vein cutting the Beck Springs Dolomite, Beck Canyon, California

Intricate contact of magnetite with surrounding dolomite, Beck Canyon, California

Comb layering in the Adamello Pluton, Italian Alps.

A magmatic contact between tonalite and enclave-rich granodiorite is offset by a magmatic shear zone, Adamello Pluton, Italy

Ductile marble flows around fractured and offset quartzite in the metamorphosed sedimentary section south of the Adamello pluton, Italy

Vesicle escape tubes in the Taos Plateau Basalt, Rio Grande Rift, New Mexico

Large modern dessication cracks, Argentine Precordillera

Syn-rift sediments, Argentine Precordillera

Colorful syn-rift sediments in the foreground of the main Andean Cordillera, Argentina