Basalt

Sunset Crater. The presence of green olivine crystals in a glassy matrix is one clue to this rock's origin. Another is its rough, spongy appearance--the result of gas escaping during eruption.

Basalt

Erupted 1943-1947. The basalt is made up of brown glass and the mineral olivine. As it erupted and cooled, escaping gas bubbles created its spongelike texture.

Basalt

The most common rock of oceanic crust, basalt erupts on the sea floor at spreading ridges.

Basalt (Volcanic bomb)

Basalt erupted in 1975-1976. A volcano spit out this clot of magma, which then twisted, cooled, and solidified during its half-minute descent. Escaping gases produced the spongy texture.

Basalt Drill Core

Depth 48.3 meters; Drill Hole 79-1 erupted 1959, sampled 1979. This sample, which was relatively close to the lake's surface, had completely crystallized by 1979.

Basalt Drill Core

Depth 51.9 meters; Drill Hole 79-1 erupted 1959, sampled 1979. At this depth, the lava still contained 18 percent liquid (now brown glass) in 1979.

Basalt Drill Core

Depth 53.1 meters: Drill Hole 79-1 erupted, 1959, sampled 1979. Deeper and hotter, the lava was 24 percent liquid (now brown glass) in 1979.

Basalt Drill Core

Depth 55.6 meters; Drill Hole 79-1; erupted 1959, sampled, 1979. Deep within the lake the lava was 31 percent liquid (now brown glass) in 1979. Notice that the black iron-titanium oxide minerals visible in the other drill core photos had not yet started to crystalize.

Basaltic Cinders

We reassembled these layered cinders as they appeared at Dotsero Volcano, a cinder cone in western Colorado. Like many cinder cones, Dotsero is quarried for construction material.

Basaltic Dike

At spreading ridges on the sea floor, new basaltic material wells up in cracks through earlier solid basalt. This glassy basaltic dike was injected into solid basalt, shouldering it aside and forcing the two tectonic plates to move apart. Hole 504B: 111-504B-142R-01A. 9-17 cm, #1B

Glassy basalt

Glassy Basalt formed into souvenir medallions while still molten.

Glassy basalt

Glassy Basalt formed into souvenir medallions while still molten.

Glassy basalt

Glassy Basalt formed into souvenir medallions while still molten.

Lunar Olivine Basalt 15555

Mare basalts from the Imbrium Basin range from 3.2 to 3.4 billion years in age, showing that volcanism in the basin lasted over 200 million years. This specimen formed midway through the epoch. Collected by Apollo 15.

Pahoehoe Lava

A geologist's hammer was singed when used to collect molten pahoehoe lava, which dripped down before freezing in the air.

Pillow Basalt

This pillow basalt erupted and cooled quickly on the sea floor. Hole 504B: 69-504B-4-4. 0-10 cm, #327

Pillow Lava

Toothpaste squeezed from a giant tube? No, this is a pillow of basalt, the most common lava erupted on the sea floor. Its thin coating of dark manganese oxide minerals was precipitated from hot mineral-rich water, perhaps with the aid of bacteria.

Volcanic Bomb

This volcanic bomb was ejected from Heimaey as a clot of molten basalt. It flattened on impact, producing a turtle-shell shape. The surface cooled quickly, forming a flaky skin.