The edge of Grand Prismatics, Yellowstone National Park, USA.
                       
The Excelsior Geyser Crater, Yellowstone National Park, USA.
                       
Fountain Paint pots, Yellowstone National Park, USA.
                       
The Echinus Geyser in the Norris Geyser Basin, Yellowstone National Park, USA.
                       
Norris Geyser Basin, Yellowstone National Park, USA.
                       
The Mud Volcano Area, Yellowstone National Park, Wyoming.
                       
Boiling mud in the Mud Volcano Area of Yellowstone National Park, Wyoming.
                       
The Mud Volcano Area, Yellowstone National Park, Wyoming.
                       
Mt Rainier, Washington State, USA from Chinook Pass.
                       
Fife Peak on the flanks of Mt Rainier, Washington State, USA
                       
Mount Lassen in Mount Lassen National Park, California
                       
Mount Shasta in Northern California
                       
Norris Geyser Basin, Yellowstone National Park.
                       
Inside a fissure in the volcano Nea Kameni, near Santorini in Greece
                       
Boats anchored off the volcanic island of Nea Kameni, near Santorini in Greece
                       
A lava field on the volcano, Nea Kameni near Santorini in Greece
                       
The crater on the volcano, Nea Kameni near Santorini in Greece
                       
The crater on the volcano, Nea Kameni near Santorini in Greece
                       
The crater on the volcano, Nea Kameni near Santorini in Greece
                       
The crater on the volcano, Nea Kameni near Santorini in Greece
                       
The crater on the volcano, Nea Kameni near Santorini in Greece
                       
The volcanic island of Nea Kameni in Greece. Taken from Thera on the island of Santorini.
                       
Vesuvius from Capri, looking across the Bay of Naples
                       
Mount St Helens, from the Information Center near Interstate 5, Washington State, USA.