It’s Volcano Week! You may not have heard of this annual celebration hosted by the National Park Service (NPS) but it’s the perfect opportunity to learn more about the lava-filled peaks that continue to shape our Earth.
There are about 1,350 potentially active volcanoes around the world, 161 of which are in the U.S. and its territories.
Volcano Week 2023 takes place February 5-11.
“Some volcanic eruptions are witnessed by people who remember what they’ve seen by writing it down, painting about it, telling stories, or collecting detailed scientific data. Other eruptions go unseen, hidden in the distant past. How do we discover, learn about, and remember those eruptions? We have to look at many lines of evidence to reconstruct the activity and eruptions of volcanoes,” the park service said.
Volcanoes are diverse! They range from the majestic Mount Rainier to colossal shield volcanoes like Mauna Loa (Hawai’i Volcanoes National Park) and volcanic fields that can cover hundreds of square miles such as at Craters of the Moon National Monument.
Some volcanoes are picturesque, others less so. They vary in size from small cinder cones that stand only a few hundred feet tall to the most massive mountains on earth. Some have textbook-perfect conical shapes and others are more irregular in form.
Some volcanoes erupt only once and last for only a few days or less while others may have periods of activity that span expanses of time as great as a few million years.
Each volcano is somewhat unique, but most can be classified into several types. The most common types of volcanoes are cinder cones, composite volcanoes (stratovolcanoes), shield volcanoes, and volcanic domes.
Several other types of volcanoes exist and are part of the diversity of volcanic landforms found on land. Examples of these volcanoes are also found in national parks.
Cinder cone volcanoes
Cinder cones are the most common type of volcano in the world. They may look like an idealized depiction of a volcano as they are steep, conical hills that usually have a prominent crater at the top. Cinder cones are the most common type of volcano in the National Park System.
Capulin Volcano and Sunset Crater Volcano national monuments were established specifically to preserve especially large and picturesque cinder cones. These volcanoes are the tallest cinder cones in the National Park System with a height of approximately 1,000 feet each. Wizard Island in Crater Lake National Park is a cinder cone that formed after the caldera-forming eruption.
At least 24 units in the National Park System contain cinder cones, including:
- Capulin Volcano National Monument, New Mexico
- Sunset Crater Volcano National Monument, Arizona
- Petroglyph National Monument, New Mexico
- El Malpais National Monument, New Mexico
- Lassen Volcanic National Park, California
Composite volcanoes
Composite volcanoes can be the most picturesque of all volcanoes. A classic composite volcano is conical with a concave shape that is steeper near the top. These mountains commonly have snow-covered peaks standing high above the surrounding mountainous terrain.
Composite cones are large volcanoes (many thousands of feet tall) generally composed of lava flows, pyroclastic deposits, and mudflow (lahar) deposits, as well as lava domes. Composite volcanoes are active over long periods (tens to hundreds of thousands of years) and erupt periodically. Composite volcanoes are also called stratovolcanoes.
Mount Rainier is an active volcano and the tallest peak in the Pacific Northwest. It is also considered to be the most dangerous volcano in the Lower 48. Brokeoff Volcano (Mount Tehama) in Lassen Volcanic National Park is a deeply eroded large composite volcano. It consisted of lava domes, lava flows, and pyroclastic deposits that are between 590,000 and 385,000 years old.
At least eight units of the National Park System contain composite volcanoes, including:
- Mount Rainier National Park, Washington
- Lassen Volcanic National Park, California
- Mount St. Helens National Volcanic Monument, Washington
- Crater Lake National Park, Oregon
- Katmai National Park, Alaska
Shield volcanoes
Although shield volcanoes are the largest volcanoes on Earth, they do not form soaring mountains with conical peaks like composite volcanoes. Instead, they are broad volcanoes with gentle slopes and are shaped somewhat like a warrior’s shield lying flat on the Earth. Shield volcanoes have a convex shape as they are flatter near the summit.
Shield volcanoes are truly massive with volumes that dwarf other types of volcanoes even large composite volcanoes. Shield volcanoes are usually constructed almost entirely of basaltic and/or andesitic lava flows which were very fluid when erupted. They are built by repeated eruptions that occurred intermittently over vast periods (up to a million years or longer).
At least 13 units of the National Park System contain shield volcanoes, including:
- Hawai’i Volcanoes National Park, Hawai’i
- Lassen Volcanic National Park, California
- Crater Lake National Park, Oregon
- El Malpais National Monument, New Mexico
- Craters of the Moon National Monument, Idaho
Volcanic Domes
Domes form from the slow extrusion of highly-viscous silicic lava. These lavas are too thick to spread out into a lava flow. Most domes are small and many do not have a crater. Domes are sometimes called lava domes.
Lassen Volcanic National Park contains multiple lava domes. Lassen Peak (see above photo) is the world’s largest dome with a peak elevation of 10,457 feet. It was emplaced 27,000 years ago. Chaos Crags are a set of six lava domes that grew during eruptions approximately 1,050 years ago. In Valles Caldera National Preserve, at least seven lava dome complexes formed along the ring fracture of the Valles Caldera during post-caldera volcanic activity.
At least 12 units of the National Park System contain volcanic domes, including:
- Lassen Volcanic National Park, California
- Valles Caldera National Preserve, New Mexico
- Big Bend National Park, Texas
- Crater Lake National Park, Oregon
- Lava Beds National Monument, California
Other types of volcanoes
Maars and tuff rings
Maars and tuff rings are low-standing volcanoes with wide, bowl-shaped craters. They commonly have a donut-like profile. Their low edifices consist of shallowly-dipping deposits of tuff made mostly of ash and angular, nonvesicular pebble-sized pyroclasts (lapilli).
A maar is a volcanic crater in which the crater lies below the surrounding ground level and is surrounded by a low pyroclastic cone. Because they are topographic lows, maars frequently contain lakes in their craters. A tuff ring is a pyroclastic cone with a crater above the surrounding ground surface. Tuff ring craters are usually dry.
At least six units of the National Park System contain maars or tuff rings, including:
- Bering Land Bridge National Preserve, Alaska
- Petrified Forest National Park, Arizona
- Big Bend National Park, Texas
- Bandelier National Monument, New Mexico
Fissure volcanoes
Fissure volcanoes are produced by eruptions that occur along elongated fissures versus at a central vent. Fissure eruptions occur when magma-filled dikes intersect the surface. Fissure eruptions usually do not build substantial edifices but instead, feed lava flows that can travel great distances. Fissure eruptions may also occur in rift zones on shield volcanoes. They also frequently occur in monogenetic volcanic fields.
Fissure eruptions may be large or small, depending on the magma supply and length of the fissure. Fissure volcanoes have been the site of the largest volume of volcanic eruptions in Earth’s history in terms of the magnitude of lava erupted.
At least four units of the National Park System contain fissure volcanoes, including:
- El Malpais National Monument, New Mexico
- Craters of the Moon National Monument, Idaho
- Petroglyph National Monument, New Mexico
- Lava Beds National Monument, California
Monogenetic volcanic fields
Volcanic fields are clusters of volcanoes or areas covered by volcanic rocks. Monogenetic volcanic fields consist mostly (or exclusively) of monogenetic volcanoes. These volcanoes (cinder cones, maars, tuff rings, and eruptive fissures) each experience one period of activity. Most monogenetic volcanic fields include areas covered by basaltic lava flows and clusters of cinders cones and/or maars and tuff rings, sometimes with a composite volcano or shield volcano located near the center of the field.
At least 13 units of the National Park system contain all or parts of monogenetic volcanic fields, including:
- El Malpais National Monument, New Mexico
- Mojave National Preserve, California
- Petroglyph National Monument, New Mexico
- Death Valley National Park, California and Nevada
- Petrified Forest National Park, Arizona
Calderas
Calderas are collapse features that form during large-volume volcanic eruptions when the underlying magma chamber is partially emptied and the ground above it subsides into it. Calderas are large, generally with a diameter greater than 0.6 miles. The largest calderas are tens of miles wide. A defining characteristic of calderas is that they have diameters that are much wider than their included vents.
At least 16 units of the National Park System contain calderas, including:
- Chiricahua National Monument, Arizona
- Aniakchak National Monument, Alaska
- Saguaro National Park, Arizona
- Big Bend National Park, Texas
- Crater Lake National Park, Oregon
Worth Pondering…
Each volcano is an independent machine—nay, each vent and monticule is for the time being engaged in its own peculiar business, cooking as it were its special dish which in due time is to be separately served. We have instances of vents within hailing distance of each other pouring out totally different kinds of lava, neither sympathizing with the other in any discernible manner nor influencing other in any appreciable degree.
—Clarence Edward Dutton, Report on the Geology of the High Plateaus of Utah (1880)