The first set of photographs was taken at Kilauea, an active shield volcano on the Big Island of Hawaii. This volcano is located over a hot spot, and is not located on a plate boundary.

    Shield volcanoes are the largest type of volcano on Earth and in the Solar System. Kilauea is so large and its slope is so gentle and gradual that many people visiting Volcano National Park at its summit don't realize that they are standing on the volcano. Park personnel say that people are always asking. "Where's the volcano?"

    This first photograph taken near the peak of Kilauea shows a former lava lake, now with a thick skin covering the still-molten magma a short distance underneath. The wispy white spots on the floor of the crater are places where steam and other volcanic gases are emerging from the magma. Visitors can take a hike along a trail crossing the lake surface.

    This photograph, taken from a helicopter, shows the vent that was active in 1996.

    Lava flows have covered roads and neighborhoods on the seaward side of Kilauea.

    Trees are killed by being overrun by a lava flow, of course, but often basalt casts of the tree trunks remain, producing  odd igneous fossils.

    Eventually, the lava flows into the sea, where it solidifies to form new, but very unstable, land.

    A lot of the lava flows underground through lava tubes. Megaera, below, has her arm in a little lava tube, but the tubes can be large enough to drive a truck through. Lava can remain molten and flow tremendous distances when insulated by a lava tube. There is a small risk of falling through active lava tubes and into the lava when walking across the Kilauea lava field, one of the reasons why the lava field is off-limits to visitors at Volcano National Park.

    Lava also flows at the surface of the volcano, where it can take one of two forms, aa or pahoehoe. In the photograph below, an aa flow is in the background and a pahoehoe flow is in the foreground. Aa is a blocky flow in which a thick skin forms on the surface of the lava, breaking up into ragged chunks as the moten material moves underneath. An advancing aa flow looks like a pile of incandescent red boulders rolling over one another, as if pushed from behind by a hidden bulldozer.
    Pahoehoe, or ropy lava, is a type of flow in which the molten material pushes the thin skin into smooth, convoluted, braided surface. Pahoehoe moves along fairly rapidly with viscous lobes oozing over one another.

    Shown below is the toe of a pahoehoe flow.

    This is what the inside of a pahoehoe lobe looks like. The holes, or vesicles, were created by gases trapped in the solidifying lava.

    Beautiful pahoehoe, solidifying to a dazzling silver color when fresh, creates a fascinating variety of forms:
 
 

    Whereas lava flows are the dominant kind of eruption on a shield volcano, explosive eruptions can also occur, producing layered tuffs as shown here. A large bomb can be seen in the middle of the photograph.

    Volcanic activity is accompanied by faulting and earthquakes. Very often, an early sign of an impending eruption is swelling of the ground over the rising magma, causing splitting of the volcano's surface. Such a fault is shown below:

    Magmas contain water vapor, carbon dioxide, sulfur dioxide (and other sulfur gases, such as hydrogen sulfide) and other irritating and dangerous fumes. On Hawaii, this material is called VOG (volcanic smog) and is a local health hazard.

    Noxious hot gases emerge from vents all over Kilauea.

    Elemental sulfur and other minerals precipitate around the steam vents.

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    This second set of photos comes from Mount Kelimutu on Flores Island in Indonesia. Indonesia is located along a complex convergent plate boundary. Kelimutu is a stratovolcano that has blown its top off, apparently several times, leaving behind a cluster of three beautiful caldera lakes. Each of Kelimutu's lakes is a different color, and the colors commonly change as circulation of water brings different materials to the surface. Local myth makes the lakes of Kelimutu the resting place of souls, with each lake being for a different group: one for children, one for criminals, and one for everyone else.

    The yellow material in the lake in the foreground below is sulfur. The lake is a concentrated sulfuric acid solution. Students like to ask if it is possible to go into the lakes. The answer is yes. But you can't get out again.

    To see more volcano photographs, go to the Pagan Volcano page. There you can see photographs of an erupting stratovolcano from the Northern Marianas.

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