Hawaii’s Kilauea volcano recently erupted like a stomp rocket

air pressure: The force exerted by the weight of air molecules.

ash: (in geology) Small, lightweight fragments of rock and glass spewed by volcanic eruptions. (in biology) A group of deciduous trees in the olive family that are popular in landscaping and for timber.

bladder: A flexible bag-like structure for holding liquids or gases.

caldera: A crater formed when a central part of a volcano collapses or by extremely forceful explosions.

compression: Pressing on one or more sides of something in order to reduce its volume.

crater: A large, bowl-shaped cavity in the ground or on the surface of a planet or the moon. They are typically caused by an explosion or the impact of a meteorite or other celestial body. Such an impact is sometimes referred to as a cratering event.

debris: Scattered fragments, typically of trash or of something that has been destroyed. Space debris, for instance, includes the wreckage of defunct satellites and spacecraft.

earthquake: A sudden and sometimes violent shaking of the ground, sometimes causing great destruction, as a result of movements within Earth’s crust or of volcanic action.

eruption: (in geoscience) The sudden bursting or spraying of hot material from deep inside a planet or moon and out through its surface. Volcanic eruptions on Earth usually send hot lava, hot gases or ash into the air and across surrounding land. In colder parts of the solar system, eruptions often involve liquid water spraying out through cracks in an icy crust. This happens on Enceladus, a moon of Saturn that is covered in ice.

frequency: The number of times some periodic phenomenon occurs within a specified time interval. (In physics) The number of wavelengths that occurs over a particular interval of time.

geological: Adjective to describe things related to Earth’s physical structure and substance, its history and the processes that act on it. People who work in this field are known as geologists.

geoscience: Any of a number of sciences, like geology or atmospheric science, concerned with better understanding Earth. People who work in this field are known as geoscientists.

groundwater: Water that is held underground in the soil or in pores and crevices in rock.

infrasound: Sound waves with frequencies below the lower limit of human hearing.

link: A connection between two people or things.

magma: The molten rock that resides under Earth’s crust. When it erupts from a volcano, this material is referred to as lava.

magnitude: (in geology) A number used to describe the relative size of an earthquake. It runs from 1 to more than 8 and is calculated by the peak ground motion as recorded by seismographs. There are several magnitude scales. One of the more commonly used ones today is known as the moment magnitude. It’s based on the size of a fault (crack in Earth’s crust), how much the fault slips (moves) during a quake, and the energy force that was required to permit that movement. For each increase in magnitude, an earthquake produces 10 times more ground motion and releases about 32 times more energy. For perspective, a magnitude 8 quake can release energy equivalent to detonating 6 million tons of TNT. (in astronomy) A measure of a star brightness.

mechanism: The steps or process by which something happens or “works.” It may be the spring that pops something from one hole into another. It could be the squeezing of the heart muscle that pumps blood throughout the body. It could be the friction (with the road and air) that slows down the speed of a coasting car. Researchers often look for the mechanism behind actions and reactions to understand how something functions.

mitigate: (n or adj. mitigation) To take action or identify features that would make something less extreme, painful or disruptive.

molten: A word describing something that is melted, such as the liquid rock that makes up lava.

network: A group of interconnected people or things. (v.) The act of connecting with other people who work in a given area or do similar thing (such as artists, business leaders or medical-support groups), often by going to gatherings where such people would be expected, and then chatting them up. (n. networking)

novel: Something that is clever or unusual and new, as in never seen before. (in literature) A work of fiction.

phenomenon: Something that is surprising or unusual.

plume: (in geology) Fluids (air, water or magma typically) that move, largely intact, in a feather-like shape over long distances.

pressure: Force applied uniformly over a surface, measured as force per unit of area.

risk: The chance or mathematical likelihood that some bad thing might happen. For instance, exposure to radiation poses a risk of cancer. Or the hazard — or peril — itself. (For instance: Among cancer risks that the people faced were radiation and drinking water tainted with arsenic.)

rocket: Something propelled into the air or through space, sometimes as a weapon of war. A rocket usually is lofted by the release of exhaust gases as some fuel burns. (v.) Something that flings into space at high speed as if fueled by combustion.

scenario: A possible (or likely) sequence of events and how they might play out.

seismometer: (also known as a seismograph) An instrument that detects and measures tremors (known as seismic waves) as they pass through Earth.

sequence: The precise order of related things within some series.

slope: (in geology) The steeply pitched side of a cliff, hill or mountain. (in mathematics) The degree to which some line rises or falls from a strictly horizontal direction. A line that appears to rise as it moves to the right has a positive slope. One that appears to fall as runs to the right has a negative slope. Vertical lines have neither. Their slope is described as undefined.

sound wave: A wave that transmits sound. Sound waves have alternating swaths of high and low pressure.

strain: (in physics) The forces or stresses that seek to twist or otherwise deform a rigid or semi-rigid object.

subsidence: A downward motion. In geology, subsidence is the downward motion of Earth’s surface. Many coastal areas are subsiding , especially where groundwater has been pumped out from beneath the surface.

subtle: Adjective for something that may be important, but can be hard to see or describe. For instance, the first cellular changes that signal the start of a cancer may be only subtly different — as in small and hard to distinguish from nearby healthy tissues.

summit: (in geology) The uppermost part of a mountain or hill, or (verb) the act of climbing and reaching that uppermost point. (in public policy) A meeting between officials of some organization or governments, often with the goal of negotiating new rules, policies or treaties.

U.S. Geological Survey: (or USGS) This is the largest nonmilitary U.S. agency charged with mapping water, Earth and biological resources. It collects information to help monitor the health of ecosystems, natural resources and natural hazards. It also studies the impacts of climate and land-use changes. A part of the U.S. Department of the Interior, USGS is headquartered in Reston, Va.

unique: Something that is unlike anything else; the only one of its kind.

vent: (n.) An opening through which gases or liquids can escape. (v.) To free gases or liquids that had been under pressure. The term can also be used to release strong, pent-up emotions, such as anger.

volcano: A place on Earth’s crust that opens, allowing magma and gases to spew out from underground reservoirs of molten material. The magma rises through a system of pipes or channels, sometimes spending time in chambers where it bubbles with gas and undergoes chemical transformations. This plumbing system can become more complex over time. This can result in a change, over time, to the chemical composition of the lava as well. The surface around a volcano’s opening can grow into a mound or cone shape as successive eruptions send more lava onto the surface, where it cools into hard rock.

volcanologist: A scientist who works on the science of volcanoes.