Natural basaltic lava flows occur in many different environments and have a wide range of morphologies that reflect the conditions during flow. Most of the lava on Earth (>60%) is erupted on seafloor along the global mid-ocean ridge system. Eruptions over millions of years, as an integral part of seafloor spreading, have paved the entire seafloor. Submarine eruptions are also important parts of the construction of volcanic island arcs at subduction zones. Despite their importance, active lava flows in these environments have only rarely been directly observed. Older seafloor flows have been widely studied, but the specific conditions that created the range of morphologies seen on the seafloor remain enigmatic. Subaerial lava flows also occur on ocean islands (Hawaii, Iceland, Reunion), continental magmatic arcs (Andes, Cascades) and giant accumulations of flood basalts in Large Igneous Provinces (LIPs, like Columbia River Basalts, Deccan Traps, Siberian Traps) and also have diverse forms. In addition, basaltic lava flows are common elsewhere in our solar system covering large tracts of the terrestrial planets, the Moon and other planetary bodies. Understanding what controls the morphology of lavas in these settings is essential in interpreting volcanic processes across this wide range of environments.
Basaltic lava flows on Earth are erupted on the mid-ocean ridge system, magmatic arcs, ocean islands, and flood basalt terranes in LIPs.
The dark lunar mare are plains of basaltic rock formed by impact melting.
Lunar lava flow produced by shock melting.
Mars is covered by extensive lavas that may have interacted with ice or dry ice.
Olympus Mons, the largest volcano in the solar system (625 km in diameter and 25 km high) is a giant basaltic volcano.
Fissure eruption at Krafla, Iceland is typical of many basaltic eruptions.
Nyirangongo Lava Lake in Africa shows the challenges of studying active lava flows.
Subaerial basaltic lava flows are commonly classified as smooth pahoehoe or jagged a’a flows (Cashman & Sparks, 2013).
Lava flows commonly grow by the accretion of overlapping lobes of lava.
Natural lavas commonly have vesicles that can influence its behavior.
Sheets and lobes of lava pile up to create extensive lava flow terranes.
Partially drained lava channel.
Partially drained lava channel.
Lava flowing over steep slopes can change morphology over short distances.
Lava tubes of various sizes create insulated conduits for the transport of lava.
Ropey, pahoehoe lavas in an Icelandic lava flow.
Jagged, a’a lava that flowed over ice at Eyajfjallajökull in Iceland.
Tindars are ridges built of fragmented lava (hyaloclastite) that interacted with ice.
Tuyas are flat-topped volcanoes that erupted under glaciers.
Most submarine (and subglacial) lavas are lumpy pillow lavas.
Pillow lavas are typical of ophiolite complexes (on-land masses of oceanic crust).
Collapsed lobate lavas are also common on mid-ocean ridges.
Thin, chaotically folded sheets of lava suggest very energetic flows.
Some seafloor lava flows form continuous tabular sheets.
