Frankincense, the resin seeping out into a cut in the tree's bark, Dhofar Mountains, Salalah, southern Oman, Middle East

April 1, 2012 - Lava flowing into Valle del Bove at Mount Etna Volcano, Italy, following paroxysmal eruption.

April 1, 2012 - Nighttime paroxysmal eruption at Mount Etna Volcano, Italy. Steam cloud rising as lava melts snow in Valle del Bove.

December 23, 2007 - Lava flowing from small tunnel on flank of Pacaya volcano, Guatemala.

December 23, 2007 - Lava flow on the flank of Pacaya volcano, Guatemala.

Close-up of lava flow, Kilauea volcano, Big Island, Hawaii.

Lava flowing into sea, Kilauea volcano, Big Island, Hawaii.

November 2006 - Lava flow during eruption of Mount Etna volcano, Sicily, Italy.

November 2006 - Lava flowing from base of hornito during eruption of Mount Etna volcano, Sicily, Italy.

November 2006 - Boulder rolling in lava flow at dusk during eruption of Mount Etna volcano, Sicily, Italy.

November 2006 - Lava flow at nightfall during eruption of Mount Etna volcano, Sicily, Italy.

November 2006 - Lava flow during eruption of Mount Etna volcano, Sicily, Italy.

November 2006 - Lava flowing from base of hornito during eruption of Mount Etna volcano, Sicily, Italy.