Maar in the context of Puy de Dôme

A phreatic eruption, also called a phreatic explosion, ultravulcanian eruption or steam-blast eruption, occurs when magma heats ground water or surface water. The extreme temperature of the magma (anywhere from 500 to 1,170 °C (930 to 2,100 °F)) causes near-instantaneous evaporation of water to steam, resulting in an explosion of steam, water, ash, rock, and volcanic bombs. At Mount St. Helens in Washington state, hundreds of steam explosions preceded the 1980 Plinian eruption of the volcano. A less intense geothermal event may result in a mud volcano.

Phreatic eruptions typically include steam and rock fragments; the inclusion of liquid lava is unusual. The temperature of the fragments can range from cold to incandescent. If molten magma is included, volcanologists classify the event as a phreatomagmatic eruption. These eruptions occasionally create broad, low-relief craters called maars. Phreatic explosions can be accompanied by carbon dioxide or hydrogen sulfide gas-emissions. Carbon dioxide can asphyxiate at sufficient concentration; hydrogen sulfide acts as a broad-spectrum poison. A 1979 phreatic eruption on the island of Java killed 140 people, most of whom were overcome by poisonous gases.

The Auckland volcanic field is an area of monogenetic volcanoes covered by much of the metropolitan area of Auckland, New Zealand's largest city, located in the North Island. The approximately 53 volcanoes in the field have produced a diverse array of maars (explosion craters), tuff rings, scoria cones, and lava flows. With the exception of Rangitoto, no volcano has erupted more than once, but the other eruptions lasted for various periods ranging from a few weeks to several years. Rangitoto erupted several times and recently twice; in an eruption that occurred about 600 years ago, followed by a second eruption approximately 50 years later. The field is fuelled entirely by basaltic magma, unlike the explosive subduction-driven volcanism in the central North Island, such as at Mount Ruapehu and Lake Taupō.

Mount Gambier, also known as Berrin, is a maar complex in South Australia associated with the Newer Volcanics Province. The complex contains four maars, the most well-known one of which is Blue Lake / Warwar. The others are Valley Lake / Ketla Malpi, Leg of Mutton Lake / Yatton Loo and Brownes Lake / Kroweratwari. The complex is partially surrounded by the city of Mount Gambier.

Blue Lake / Warwar (The Blue Lake) is a large, monomictic, crater lake located in a dormant volcanic maar associated with the Mount Gambier maar complex. The lake is situated near Mount Gambier in the Limestone Coast region of South Australia, and is one of four volcanic crater lakes originally on Mount Gambier maar. Of the four lakes, only two remain, the other one being Valley Lake / Ketla Malpi; the other two, Leg of Mutton Lake / Yatton Loo and Brownes Lake / Kroweratwari, dried up as the water table dropped.

A monogenetic volcanic field is a type of volcanic field consisting of a group of small monogenetic volcanoes, each of which erupts only once, as opposed to polygenetic volcanoes, which erupt repeatedly over a period of time. The small monogenetic volcanoes of these fields are the most common subaerial volcanic landform.

Many monogenetic volcanoes are cinder cones, often with lava flows, such as Parícutin in the Michoacán-Guanajuato volcanic field, which erupted from 1943 to 1952. Some monogenetic volcanoes are small lava shields, such as Rangitoto Island in the Auckland volcanic field. Other monogenetic volcanoes are tuff rings or maars. A monogenetic field typically contains between ten and a hundred volcanoes. The Michoacán-Guanajuato field in Mexico contains more than a thousand volcanoes and is exceptionally large.

The Volcanic Eifel or Vulkan Eifel (German: Vulkaneifel) consists of three areas of volcanic activity, known as the West Eifel, High Eifel, and East Eifel volcanic fields. Volcanic Eifel is a region in the Eifel Mountains in Germany that is defined to a large extent by its volcanic geological history. Characteristic of the volcanic fields are their typical explosion crater lakes or maars, and numerous other signs of volcanic activity such as volcanic tuffs, lava streams and volcanic craters, for example the Laacher See. The Volcanic Eifel is still volcanically active today. One sign of this activity is the escaping gases in the Laacher See.

The Monti Sabatini is a geologic region in Lazio, central Italy, a remnant of intense volcanism which started ca. 600,000 years ago, mainly with pyroclastic and maar forming eruptions which continued until 100,000 years ago. The region is classified as a dormant volcanic district. The mountains are part of the Lazio's Anti-Apennines. Included between the Monti Sabatini is the Lake Bracciano, which is a volcanotectonic depression formed about 3.7 Ma, and the Lake Martignano. The sedimentary base of the Sabatini complex lies buried under 200 m (660 ft) of volcanic ash and rocks.

The Bering Land Bridge National Preserve is one of the most remote protected areas of the United States, located on the Seward Peninsula. The National Preserve protects a remnant of the Bering Land Bridge that connected Asia with North America more than 13,000 years ago during the Pleistocene ice age. The majority of this land bridge now lies beneath the waters of the Chukchi and Bering Seas. During the glacial epoch this bridge was a migration route for people, animals, and plants whenever ocean levels fell enough to expose the land bridge. Archeologists debate whether it was across this Bering Land Bridge, also called Beringia, that humans first migrated from Asia to populate the Americas, or whether it was via a coastal route.

Bering Land Bridge National Monument was established in 1978 by Presidential proclamation under the authority of the Antiquities Act. The designation was modified in 1980 to a national preserve with the passage of the Alaska National Interest Lands Conservation Act (ANILCA), which would allow both subsistence hunting by local residents and sport hunting. The preserve includes significant archaeological sites and a variety of geological features. The preserve has seen recent volcanic activity, with lava flows and lake-filled maars. Hot springs are a popular destination for tourists.