iTechGuides is reader-supported. When you buy through links on our site, we may earn an affiliate commission. As an Amazon Associate I earn from qualifying purchases. Learn more
Lava fountains are sprays of molten rock driven upward when gas dissolved in rising magma expands as pressure falls. Geysers are hydrothermal eruptions: groundwater heated underground flashes partly into steam and ejects liquid water, steam, and spray. They may occur in the same broad volcanic regions, but one is a magmatic eruption and the other is a water-and-steam event.
What a lava fountain is
The National Park Service defines a fire fountain, another name for a lava fountain, as “A spray of molten lava propelled a few tens to hundreds of feet (meters) into the air by rapid expansion of gas bubbles.” The ejected material is therefore molten rock, not heated groundwater. The gas is magmatic: it was dissolved in the melt while the magma was under pressure underground. The NPS anatomy-of-a-volcano guide uses the term fire fountain, while the NPS volcanic-eruptions guide places fountaining among eruption behaviors.
Fountaining is most strongly associated with low-viscosity basaltic magma and Hawaiian-style, or effusive, eruptions. Basalt can flow readily enough for gas bubbles to rise and expand rather than becoming trapped in a thick, fragmented magma mass. That association is common, not exclusive: crystal content, temperature, gas composition and amount, interaction with water, and the total amount and rate of erupted material all influence the resulting eruption. The U.S. Geological Survey’s eruption-styles overview describes these controls.
How expanding magmatic gas creates a fountain
A fountain develops through a linked sequence of pressure, bubble, and flow changes:
#1 Best Overall
- Read Before You Buy — No Video Output: These adapters support charging and USB 2.0 data transfer, but cannot transmit video signals. Except for standard USB webcams (which use USB data only), they are not compatible with HDMI/DisplayPort cables, video-capable USB-C hubs, or docking stations with video output.
- Convert USB-A Ports to USB-C: Designed to connect USB-C earphones, cables, flash drives, card readers, and other USB-C accessories to standard USB-A ports. Plug-and-play with no drivers or software required.
- Aluminum Alloy Housing: Built with a sturdy aluminum alloy shell that aids in heat dissipation and protects against daily wear and scratches. Designed to maintain a stable and secure connection.
- Compact & Travel-Friendly: The ultra-compact design allows the adapter to stay plugged into your device without blocking adjacent ports or adding bulk, reducing wear and tear on your original USB ports.
- 12-Month Warranty: Backed by a 12-month manufacturer warranty for peace of mind. Designed to meet strict quality control standards for reliable everyday performance.
- Volatiles are dissolved at depth. Magma contains volatile gases, including water vapor, carbon dioxide, and sulfur-bearing gases. High confining pressure keeps much of that gas dissolved in the melt.
- Magma ascends. As magma moves up a conduit or fissure, the surrounding pressure decreases.
- Vesiculation begins. With less pressure holding gas in solution, dissolved gas exsolves and forms bubbles. This bubble-forming process is called vesiculation.
- Bubbles expand. The bubbles occupy more volume as pressure continues to fall. Their expansion can accelerate the surrounding melt.
- The mixture exits a vent. Rapidly expanding bubbles propel molten lava into the air. Droplets and blobs follow ballistic paths before falling back around the vent or into a lava flow.
The USGS compares the pressure release to opening a carbonated drink: a sudden release produces vigorous foaming and spray, whereas slower gas escape allows quieter behavior. The analogy captures the pressure effect, but an actual fountain also depends on magma viscosity, temperature, crystals, conduit geometry, gas chemistry, and the rate at which magma and gas reach the surface. USGS Hawaiian Volcano Observatory’s explanation of lava fountains discusses the competing processes.
There is more than one gas-release pathway
Scientists do not use a single universal model for every fountain. Two pathways described by USGS help explain why different eruptions can look different.
Near-surface bubble growth
In one model, magma rises quickly and bubbles exsolve close to the surface. Gas expansion then accelerates the upper magma column and produces a fountain near the vent. The exact depth and timing depend on the magma’s volatile content, ascent rate, and physical properties.
The Tool Desk
Outbyte PC Repair FREEClear out junk files and repair common Windows errorsFree Scan →Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →Deeper gas separation and a rising pocket
In another model, gas separates from the melt deeper underground and gathers into foam. The foam can collapse into a large gas pocket that rises rapidly, carrying or pushing magma around it. This process can deliver a concentrated burst of gas to the surface rather than a steady stream of newly formed shallow bubbles.
Rank #2
- 5-in-1 USB-C Hub: Experience comprehensive connectivity featuring a Power Delivery input, two USB-A 2.0 ports, a USB-A 3.0 port, and an HDMI port. (Note: The USB-C power delivery input port is only for connecting an external wall charger to power your laptop and cannot power peripheral devices.)
- 90W Pass-Through Charging: Achieve optimal charging with 90W pass-through power to your laptop, supported by a total input of 100W, with the hub reserving 10W for operational efficiency. (Note: Wall charger not included.)
- Quick Data Transfers: Accelerate your productivity with rapid data transfers using a high-speed 5Gbps USB 3.0 port and two 480Mbps USB 2.0 ports.
- 4K HDMI Display: Enhance your visual experience with a hub capable of delivering 4K resolution at 30Hz in both mirror and extend modes. Please note that this hub is compatible with MacBook (macOS 12 and newer), Windows 10 and 11, ChromeOS, and laptops equipped with DP Alt Mode and Power Delivery. Note: This device is not compatible with Linux.
- What You Get: Anker USB-C Hub (5-in-1, 4K HDMI), welcome guide, 18-month warranty, and our friendly customer service.
What the Mount Etna evidence shows
During 64 lava-fountaining episodes at Mount Etna’s southeast crater between January and June 2000, gas-composition observations were interpreted as evidence that the gas phase formed and reached equilibrium at roughly 1.5 kilometers depth before ascending rapidly. The episodes reached a reported maximum height of up to 3,000 feet. That interpretation applies to the Etna activity studied by the HVO account; it is not a rule that every fountain forms its gas at 1.5 kilometers. The case is reported in this USGS Hawaiian Volcano Observatory article.
Why some basaltic eruptions fountain while others do not
Gas expansion supplies the immediate lift, but the visible style depends on the whole magma-and-vent system. Important controls include:
- Viscosity: Low-viscosity basalt generally permits bubbles to move and expand efficiently, favoring Hawaiian-style fountaining. More viscous magma can hinder bubble escape and promote different eruptive behavior.
- Temperature: Hotter magma is usually more fluid, while cooling can increase resistance to flow and alter bubble movement.
- Crystal content: Crystals make the magma mixture mechanically more complicated and can change how bubbles rise, merge, or become trapped.
- Gas composition and quantity: Water vapor, carbon dioxide, and sulfur-bearing gases have different solubilities and affect when and how exsolution occurs.
- Ascent and discharge rate: The amount and rate of material reaching the vent influence whether gas is released gradually or in bursts.
- Water interaction: External or underground water can change heat transfer, fragmentation, and eruption dynamics, so not every gas-driven event has the same appearance.
These factors explain why a fountain’s appearance cannot be reduced to one variable such as gas percentage or height. They also explain why two episodes at the same volcano can alternate between vigorous jets, lower spattering, and lava-flow production.
What a geyser is and how it erupts
A geyser is a hydrothermal feature rather than a vent ejecting magma. Surface water percolates downward through porous rock, fractures, and underground passages. Geothermal heat—often associated with magma or very hot rock—raises the water’s temperature. Heated water then moves through a plumbing system toward the surface.
Rank #3
- Sleek 7-in-1 USB-C Hub: Features an HDMI port, two USB-A 3.0 ports, and a USB-C data port, each providing 5Gbps transfer speeds. It also includes a USB-C PD input port for charging up to 100W and dual SD and TF card slots, all in a compact design.
- Flawless 4K@60Hz Video with HDMI: Delivers exceptional clarity and smoothness with its 4K@60Hz HDMI port, making it ideal for high-definition presentations and entertainment. (Note: Only the HDMI port supports video projection; the USB-C port is for data transfer only.)
- Double Up on Efficiency: The two USB-A 3.0 ports and a USB-C port support a fast 5Gbps data rate, significantly boosting your transfer speeds and improving productivity.
- Fast and Reliable 85W Charging: Offers high-capacity, speedy charging for laptops up to 85W, so you spend less time tethered to an outlet and more time being productive.
- What You Get: Anker USB-C Hub (7-in-1), welcome guide, 18-month warranty, and our friendly customer service.
The USGS describes the final eruption cautiously because geyser plumbing is complex and not completely understood. A substantial volume of hot water is presumed to occupy underground cavities. When conditions change, some of that water can suddenly flash into steam. The rapid expansion of steam violently ejects the remaining liquid water and steam through the opening. The ejected material is therefore water in liquid and vapor forms, not molten rock. The mechanism and timing vary among geysers because each has its own fractures, cavities, heat supply, and water recharge. See USGS, “Volcanoes: Geysers, Fumaroles, and Hot Springs.”
Both phenomena involve expansion and pressure, which can make photographs look superficially similar. Their energy sources and materials are different: a lava fountain is powered by decompression of ascending magma, while a geyser is powered by geothermal heating of groundwater and steam formation within a hydrothermal system.
Lava fountains and geysers compared
| Comparison | Lava fountain | Geyser |
|---|---|---|
| Material ejected | Molten rock (lava) mixed with magmatic gas | Heated groundwater, liquid water, and steam |
| Main driving process | Magma ascent and expansion or exsolution of dissolved gas as pressure falls | Geothermal heating and sudden flashing of some water into steam |
| Typical setting | Volcanic vent or fissure, commonly during basaltic, effusive activity | Water-fed hydrothermal plumbing in a region with geothermal heat |
| What controls the visible event | Magma viscosity, temperature, crystals, gas chemistry and amount, ascent and discharge rates, water interaction, and bubble behavior | Underground water volume, heat, cavities, fractures, recharge, and the details of a plumbing system that remain incompletely understood |
| Interpretive caution | Different gas-separation pathways can produce fountains; height alone is not a simple gas-content gauge | Eruption details vary, and the complete geyser mechanism is not established |
Why fountain height is not a simple gas gauge
A taller fountain can look as though it must contain more gas, but height alone does not establish the magma’s gas content. A USGS-indexed study by E. A. Parfitt, L. Wilson, and C. A. Neal identified magma gas content, volume flux, lava re-entrainment, and gas-bubble coalescence as controls on Hawaiian fountain height. In the studied Puʻu ʻŌʻō episodes, changes in volume flux and the amount of lava thrown back into the fountain could explain much of the height variation even when gas content was broadly constant. The study is summarized at USGS Publications Warehouse.
Free tools Windows power users keep installed
One-click scans. No signup required.
“The heights of lava fountains formed in Hawaiian-style eruptions are controlled by magma gas content, volume flux and the amounts of lava re-entrainment and gas bubble coalescence.” — E. A. Parfitt, L. Wilson, and C. A. Neal, 1995.
Rank #4
Sale
UGREEN USB to USB C Adapter Combo 4-Pack, 10Gbps USB C Converter Space Gray | Data transfer & Fast charging for MacBook, iPhone 17/16/15, iPad, Samsung Galaxy, Apple Watch
- Dual Converters, Infinite Potential：Includes 2× USB C male to USB A female adapters and 2× USB A male to USB C female adapters. Perfect for a wide range of uses—tablets with Bluetooth keyboards, expand USB ports on macbook, and more. Two different converters for all your daily needs
- Next-Level 10Gbps & 3A Charging: No more slow 480Mbps, this usb to usb c adapter has a transfer speed of up to 10Gbps, allowing you to do more transferring in less time. This usb adapter fits both USB A and USB C charger, supporting up to 3A fast charging
- Upgraded Exquisite Craftsmanship: With an aluminum alloy housing and metal connector, the usbc to usb adapter is extremely durable and sturdy. Rigorously tested to withstand more than 10,000 times of plugging and unplugging, ensuring long-lasting performance
- Broad Compatible: The usb c to usb adapter widely supports all USB C/ USB A devices like laptops, tablets, cellphones, car chargers, and phone chargers. Such as compatible with MacBook Pro/Air 2023/2022, Thunderbolt 4/3 Devices,Apple MagSafe Watch 9/8/7/SE/Ultra, iPad Pro 2022/2021, Samsung Galaxy S23/S20/S10, and iPhone 17/16/15 Pro. Plug and play
- Please Note: To reach 10Gbps speed, keep the cable under 3.3 ft. For USB A Male to USB C adapters, try flipping the USB C connector. USB C Male to USB A adapters support bidirectional 10Gbps transfer within 3.3 ft
That same study reported an apparent decline of about 0.05 weight percent in gas content during the final ten episodes of the eruption series it examined. The authors attributed the decline to more extensive pre-eruption degassing. The figure belongs to those specific episodes and should not be treated as a typical decline for all volcanoes or all fountains.
What the individual height factors mean
- Gas content supplies potential expansion, but only the gas that exsolves and participates in the erupting mixture contributes directly to lift.
- Volume flux is the rate at which magma reaches the vent. A faster-moving magma column can produce a higher jet without a proportional increase in dissolved gas.
- Lava re-entrainment occurs when erupted lava falls back into the fountain and becomes part of the moving mixture, changing its mass and momentum.
- Bubble coalescence combines smaller bubbles into larger gas structures, altering how expansion is distributed through the conduit and jet.
Reading the two phenomena in the field
The most reliable first question is what is being expelled. Glowing or incandescent molten fragments and a developing lava flow indicate a magmatic process consistent with fountaining. A column or burst of liquid water and steam from a water-fed vent indicates a hydrothermal process consistent with a geyser. Color, plume shape, or height alone is less diagnostic because both expanding gas and steam can create spray and rising vapor.
Next, consider the plumbing described for the feature. A volcanic vent or fissure carrying magma points toward a lava fountain. A system fed by groundwater moving through heated rock points toward a geyser. A volcano can host both kinds of activity in the same region, but their physical pathways remain distinct: magma travels through volcanic conduits, while geyser water circulates through hydrothermal cavities and fractures.
Quick wins for a faster PC:
Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Repair Windows errors before they cause bigger problemsFix Now →Scan for outdated or missing drivers - takes under a minuteDriver Scan →Finally, avoid inferring a precise subsurface gas concentration from a single photograph or measured height. Gas separation depth, volume flux, re-entrainment, and bubble coalescence can all change the appearance. Interpreting a particular episode requires observations of its gas chemistry, discharge, and setting, such as the Mount Etna analysis described above.
Best Value
- 5-in-1 Connectivity: Equipped with a 4K HDMI port, a 5 Gbps USB-C data port, two 5 Gbps USB-A ports, and a USB C 100W PD-IN port. Note: The USB C 100W PD-IN port supports only charging and does not support data transfer devices such as headphones or speakers.
- Powerful Pass-Through Charging: Supports up to 85W pass-through charging so you can power up your laptop while you use the hub. Note: Pass-through charging requires a charger (not included). Note: To achieve full power for iPad, we recommend using a 45W wall charger.
- Transfer Files in Seconds: Move files to and from your laptop at speeds of up to 5 Gbps via the USB-C and USB-A data ports. Note: The USB C 5Gbps Data port does not support video output.
- HD Display: Connect to the HDMI port to stream or mirror content to an external monitor in resolutions of up to 4K@30Hz. Note: The USB-C ports do not support video output.
- What You Get: Anker 332 USB-C Hub (5-in-1), welcome guide, our worry-free 18-month warranty, and friendly customer service.
Common misconceptions resolved
“A geyser is a small lava fountain.”
No. The visual resemblance comes from rapid expansion, but a geyser ejects heated groundwater and steam. A lava fountain ejects molten rock propelled by expanding magmatic gas.
“Every lava fountain forms gas bubbles at the surface.”
No. Gas may exsolve close to the surface, or it may separate deeper down, form a foam, collapse into a larger pocket, and rise rapidly. The applicable pathway must be evaluated for the volcano and episode.
“The highest fountain had the most gas.”
Not necessarily. The 1995 Hawaiian study found that flux, lava re-entrainment, and bubble coalescence can change height even when gas content is broadly constant.
Outdated Drivers Are Slowing You Down
One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchPC Slower Than It Used to Be?
A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11“A volcanic region’s water feature must be part of the eruption.”
Not automatically. Geysers are hydrothermal features whose water is heated underground. Their presence reflects a geothermal plumbing system, not the ejection of magma from the vent.
Key points to remember
- Lava fountains begin with dissolved magmatic volatiles and falling pressure as magma rises.
- Vesiculation creates bubbles; rapid bubble expansion propels molten lava through a vent.
- Low-viscosity basalt commonly supports Hawaiian-style fountaining, but temperature, crystals, gas chemistry, water interaction, and discharge rate also matter.
- Geysers heat groundwater in a hydrothermal system; some water flashes to steam and ejects liquid water and vapor.
- Fountain gas can separate near the surface or deeper underground. The Mount Etna 2000 interpretation placed gas-phase formation and equilibration at about 1.5 kilometers depth for that case.
- Fountain height is a combined result of gas content, volume flux, lava re-entrainment, and bubble coalescence, not a standalone gas-content measurement.
Further reading
For broader background on volcanoes, hot springs, fumaroles, and geysers, consult the USGS Volcanoes guide. The NPS pages on volcano anatomy and volcanic eruptions provide additional terminology and eruption context.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
