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Science: Background


Lava flows are among the most dramatic natural phenomena. They are unpredictable, commonly occur in remote areas and they are dangerous. Each lava flow is a unique event: an “experiment by Nature” that is difficult to study and that cannot be repeated. In the Syracuse University Lava Project lava flows are created under controlled conditions to help better understand the dynamics of flowing lava and how to interpret lava flows from the geologic record.

There are many factors that influence the behavior of lava including composition (especially silica content), temperature, slope, effusion rate, vesicularity (entrained gas bubbles), crystallinity, water content and the nature of the surface that the lava flows over. In our experiments, we attempt to hold as many of these factors constant as possible as we vary one or more of the others in order to better understand their mutual effects. For example, for most of our experiments to date we use the same composition material (basalt with about 50% silica- the most common type of lava on Earth) as we systematically vary the other parameters. Observations of active lava flows in nature provide many testable hypotheses in this rich experimental environment.

Most lava flows are seen long after they have cooled and stopped flowing. Geologists seek to understand the conditions under which they erupted retroactively based on preserved features and comparisons with active flows. The composition of lava flows and their morphology (outcrop-scale form) are key elements in these interpretations. In our experiments with basaltic lava we can produce many different morphologies corresponding to those in natural lava flows. Our experiments can shed new light on the critical factors that determine the ultimate form of lava flows and how they are interpreted.

 

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. 


Click on an image to see an expanded view.


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.
Crystals that form in lava can increase its viscosity.
Sheets and lobes of lava pile up to create extensive lava flow terranes.
Typical pahoehoe lava in an Icelandic lava flow.
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.

There have been many attempts to conduct experiments with real lava and with analog materials. Probably the first was James Hall who melted basaltic (“trap rock”) with a blacksmith’s forge in ~1800. He did a number of experiments very similar to those of the early days of the Lava Project. In order to investigate the physical properties and petrology of lava small amounts of molten material is produced under controlled conditions in experimental laboratories. In order to better understand flow dynamics, scalable experiments are also commonly conducted using viscous analog materials such as Polyethylene Glycol (PEG) wax. All of these important approaches to understanding lava flow, but there is no substitute for experiments with real lava under conditions that closely match those of natural flows. 


Click on an image to see an expanded view.


James Hall, probably the first to experiment with molten basalt.
Small droplets of lava provide basic information on lava properties (Philpotts, 1996).
Experiments PEG wax provide flow analogs for lava (Gregg & Fink, 1996).