Volcanos, Lava, and Simulations in Houdini
Volcanoes are the structures that help shape the surface of the earth.
They have helped create 80% of the planet’s surface. The force from a volcano can create mountains, create cracks in the surface of the Earth, lava rivers, and much more. There are volcanoes on every continent in the world. Around 1,500 volcanoes in the world are active, and about 10% of them are in the United States.
They are ruptures in the crust of a planetary object, and because of this, it means they can be located on any planet in the Universe. They generally spew lava, volcanic ash, and other gases stored under the Earth’s crust.
They are mostly found where the Earth’s tectonic plates are diverging or converging. However, a large chunk of them are found underwater. When you hear of the Mid-Atlantic Ridge or The Pacific Ring of Fire, these areas are areas that contain underwater volcanoes. Which again were formed by divergent tectonic plates.
Our planet’s lithosphere is always shifting and bumping into other pieces of itself. When they collide, one of them will plunge under the other into what we call the subduction zone. The temperatures are often extreme in this zone, and when these collision events happen they release magma.
Volcanoes can also form where the crust of the Earth is stretching, or is very thin. Usually, this is caused by wells of volcanic material trying to push itself upwards. These volcanic areas are very isolated to themselves, and are just pockets of lava waiting to be pushed out of a volcano. This is something called hotspot volcanism.
As you might have guessed, volcanoes are involved in plate tectonics. Earth’s lithosphere is considered the most rigid outer shell of our planet. It is currently broken up into 16 larger plates and some smaller ones.
Each volcano has its own unique eruption pattern. Some just burp up lava, while others have very violent eruptions. This all comes down to what chemical reaction is going on in the volcano’s molten core. If the magma of a volcano is less viscous, then the explosion will be considered effusive. An effusive eruption is one that has lava flowing out of it straight away. With the lava out of the way, the volcano is free to release all the gas inside of it.
An explosive eruption is a bit different. This happens when the lava and molten rock traps gases under the volcano. With nowhere to go, these gases build up, and pressure builds under the Earth’s surface. Then the volcano blows up.
75% of the world's volcanoes are located in a region called The Ring of Fire. This zone stretches for over 25,000 miles. It is located between the southern tip of South America, the West Coast of North America, and through the Bering Sea to Japan. As well as through New Zealand.
Some Facts on Plate Tectonics
There are some interesting theories to plate tectonics so let's cover them.
Each plate boundary generates its own unique geological processes and landforms. At divergent boundaries, the plates of the Earth separate. They can spurt hot water, magma, molten rock, and gases. These elements then solidify into basalt, and form new matter on the earth’s crust.
Divergent Plate Boundaries:
These events are best observed at the bottom of the seafloor. When two plates diverge from each other, hot mantle rock sneaks up in between them. This also leads to the rock around it melting, the creation of new ocean crust, and volcanism. In these divergent areas, black smokers, volcanic islands, and deep sea vents are found.
Convergent Plate Boundaries:
These are the opposites of divergent plate boundaries. This phenomena happens in subduction zones. These are zones where a continental plate and an oceanic plate collide. The oceanic plate subducts, which are forced under the continental plate, then form deep ocean trenches. This process also causes something called flux melting to occur. This releases water from subducting plates and lowers the overall melting points of surrounding plates. However, this also helps the production of magma. This magma is often filled with silica based particles. Chains of volcanoes line these areas in something called volcanic arcs.
We’ve mentioned hotspots above. So here is a deeper dove into them. These volcanic hotspots are thought to be formed by mantle plumes from the core-mantle area of the Earth. These columns of hot material have nowhere to go but up, and then form volcanoes on top of them. However, as we know tectonic plates move around. Whenever they move on top of one of these magma plumes, the volcano on top of them becomes inactive. Then, when the plate moves away, new volcanoes are created.
When magma and mantle rock is pushed upwards under a plate it becomes trapped. With no gap or crack in the plate to escape from, it starts to increase a build up of pressure until the tectonic plate splits apart. Then a new divergent plate is created.
Underwater volcanoes are also known as submarine volcanoes. They are vents of fissures in the Earth’s surface, and look a bit different from what you would consider a traditional volcano. They are located in mid-ocean ridges. (tectonic plate formation areas) They account for about 75% of the magma output of Earth. There is thought to be well over a million undocumented underwater volcanoes currently on the ocean floor.
Most of these volcanoes are located in deep areas of the ocean. However, some of them are located in the shallows. The Kolumbo submarine volcano was one of these. It was only discovered when it erupted in 1650, and forever reshaped the Santorini coastline.
The majority of submarine volcanoes are seamounts. These are extinct volcanoes that rise out of the seafloor. They are around 1,000-4,000 meters high. Their surrounding peaks are often found hundreds of thousands of meters below the surface of the ocean. There are around 30,000 of these seamounts currently in existence around the globe.
One of the world’s largest volcanoes is called Havre. It exists 3,000 meters under the Pacific ocean. For about 90 days in 2012 lava poured out of it and its 14 surrounding vents. It is the largest deep water eruption ever recorded.
The way underwater volcanoes shape the surface of the Earth is very different from the way their counterparts on the surface do. Ones on above water have the luxury of releasing their gases and debris into the atmosphere, and having the pressure inside them released all at once. Ones under the ocean aren’t so lucky. They are under constant amounts of pressure from the surrounding ocean water, and sometimes experience pressure between 92-122 times that of sea level. This constant pressure dampens their explosions and the way their debris is scattered. It also shapes how lava is formed. When lava comes into contact with the water it instantly solidifies, versus in air where it takes time to cool.
There are some signature traits that make up most volcanoes on the planet. As well as some unique varieties of them.
These are flat, linear fractures that lava emerges from.
These are volcanoes that have very broad shield-like shapes. They are formed from low-viscosity lava, and do not have large dramatic explosions. These volcanoes are mostly found in the ocean, and in areas like Iceland.
These are built when highly viscous lava flows away from the volcano. They are sometimes formed in the crater of a previous volcanic eruption, but can also form by themselves. They produce violent, explosive eruptions.
These are formed when viscous lava is forced upwards and causes a bulge in the Earth’s surface.
These are volcanoes that when they erupt, have large amounts of scoria and pyroclastics build up around their vents. Scoria is a type of lightweight black or green volcanic rock with holes in it. Pyroclastics are fast moving solidified lava pieces that are projected away from the explosion. When both of these pieces fall away from the event, they appear to look like cinders.
Based on satellite images scientists have suggested that these types of volcanoes exist on other worlds in our Solar System.
Volcanic Land Formations
Here are features of land development caused by volcanoes.
These are bowl-shaped areas in the ground caused by collapsing volcanoes. When a magma chamber of a volcano is emptied, the ground around it crumbles. There are three types of calderas. A crater lake caldera happens when a stratovolcano collapses into its magma chamber. A basaltic caldera is a caldera with a ring pattern around it. This is caused by gradual collapses. Resurgent calderas are the largest volcanic structures on Earth. They are the result of massive eruptions, or “super volcanoes.”
When magma solidifies in a volcanic fissure it forms what is basically the “neck” of the volcano. It essentially plugs the volcano, and creates very straight, and almost tree stump shaped landmarks.
These are also known as Maars. They are thought to be created by expansions of magmatic gases or steam. They resemble mountains with little dips at the top. They range from 200-6,500 feet, and are filled with water which helps form surrounding lakes.
When shield volcanoes erupt they sometimes form lava plateaus. They mainly explode from various surrounding fissures and the lava starts to layer around these openings. Over time, these solidified lava layers form plateaus and then massive canyons.
Time to learn about lava. There are main different types of lava, so let’s break them down.
Lava is molten rock that has been expelled from the center of a planet. Magma is generated by the internal heat of the planet, and it usually melted to a boiling 800-1,200 degrees celsius. The rocks resulting from the cooling of this molten rock are also referred to as lava.
Most lavas contain crystals of minerals, exotic rocks, and previously solidified lava. Because of these crystals , they are given very unique shear and thinning properties. They are not considered Non Newtonian fluids. Instead they are considered Bingham fluids. Bingham fluids are fluids that show resistance until they reach a certain stress threshold. This stress is called yield stress.
A lava flow is an outpouring of lava from an eruption from a planetary surface. Lava can be up to 100,000 times more viscous than water, but it can also flow great distances rapidly and before it cools. Lava that is exposed to air develops a solid crust around it. This crust insulates the lava that is still in its liquid form.
Lava flow speeds are based on viscosity and slope. They typically have a speed of 0.25 mph (0.40km/h). The scaling relationship of lavas regarding velocity is a square of its thickness and divided by its viscosity.
The word lava comes from the latin word labes. Which means to fall or to slide. The first account of the word being used for describing lava was in 1737, during the eruption of Mount Vesuvius.
There are many different types of lava:
Silicate lavas are molten lava mixtures made up of oxygen and silicon. They are the Earth’s most abundant elements. It is also made up of smaller quantities of aluminium. Calcium, magnesium, iron, sodium, and potassium. The physical properties of this lava type are dictated by its chemical composition. Silicon ions in lava bind extremely well to oxygen ions. Depending on how many silicon and oxygen ions bind together, and in which combination, it can polymerize the lava. The more polymerized the lava is, the more viscous it will become.
Because silica plays such a huge role in determining the viscosity of lava, it’s temperature, and other properties, silicate lavas are divided into four separate groups. These groups are: felsic, intermediate, mafic, and ultramafic.
Felsic lava is a type of lava with a silica content higher than 63%. This category also includes rhyolite and dacite lavas. These lavas are extremely viscous, and are also extremely hot. Their temperature ranges around 1,200-800 degrees celsius. It usually erupts explosively from volcanoes, and produces very fragmental deposits. Rhyolite lava flows usually form lava spines and domes.
These are lava flows that contain 52%-63% of silica. They contain less aluminium than other types of lava, and they are also richer in magnesium and iron than others. They form on steep composite volcanoes, such as ones in the Andes. They are also hotter than other types of flows. Their temperatures range from 850-1,100 degrees celsius. Its viscosity is around the same as peanut butter. Peanut Butter Lava...Woooooooo!
This type of lava has a silica content around 52%-45%, and is also known as basaltic lava. They have an extremely high ferromagnesian content. (iron and magnesium) They erupt at temperatures around 1,100-1,200 degrees celsius. Their viscosities are low, and they flow about the same way as ketchup. This lava type helps form shield volcanoes, and flood basalts. Underwater, they form something called pillow lava.
These lavas are high in magnesium. They also help form the mineral boninite. They have extremely violent eruptions. They have a silica content under 45%, and contain up to 18% magnesium oxide. Their temperatures sit around 16,000 degrees celsius. They do not polymerize, and are very fast moving. Their viscosity is the same as motor oil.
These lavas contain a high amount of alkali metal oxides. (Mainly sodium and potassium) They are mostly found in regions of continental rifting, deeply subducted plates, or in hotspots. They are generated very deep in the Earth’s mantle.
Let’s take a look at some scientific simulations of lava flows and volcanoes. Starting with some scientific software.
Lava simulations have been used as far back as 1990. FLOWFRONT was a program used to help simulate these flows. It is a C program that simulates non-newtonian fluids, which lava was considered for a long time. It works in tandem with topographic slopes and thickness maps of the flow. The only downside with using FLOWFRONT with lava flows is it is unable to simulate the thermo chemical composition of lava.However, the simulations of lava in FLOWFRONT were very customizable. They allowed the users to set slope, thickness, and volume parameters. As well as simulate different types of flows from one volcanic location.
Lava simulations are incredibly useful to have, and have many different purposes. One major use for these flows is lava flow hazard modeling. This is a useful tool for scientists and the general public to predict the dangers of lava and long term hazards for areas. They can even be used to plan for city evacuations during a volcanic emergency.
Some scientists have also started to develop open source toolkits for lava flows. NASA has built one for themselves to be flexible, more customizable, and predictable than standard toolkits. This GIS toolkit operates with Digital Elevation Models (DEM) with existing probabilistic (VORIS) and deterministic (FLOWGO) systems. It is a current open source project that also runs on Python, with various customizable scripts.
Other lava simulations lean into computational fluid dynamics very heavily. There are several numerical simulations of lava flow placement out there, and CFD has been used to help create other fluid flow programs such as: VolcFlow, OpenFOAM, FLOW-3D, COMSOL, and MOLASSES. Using CFD you can accurately showcase the viscosity, cooling, sloped surfaces, and other traits of lava flows.
For islands around the world, simulating how their volcano might erupt can be live saving. So many simulations have been done to create volcanic hazard maps. For example, for Mount Etna in Italy, and volcanic ranges in Japan. These hazard maps take into account what the current terrain looks like, and how the lava will interact with the surrounding area.
Volcano and Lava Simulations in 3D Software
Creating lava simulations in VFX isn’t as tricky as creating them scientifically. But they can be difficult to pull off.
There are plenty of lava tutorials out there on Youtube, both in Blender and Houdini. Here are two you can check out.
- Blender Tutorial: Lava Simulation With Procedural Texture: https://www.youtube.com/watch?v=t90JwLLsS60
- Tutorial 25 - Houdini Lava Like a Boss (Part 1): (ben watts): https://vimeo.com/126886471
It’s important to make sure your lava simulation preserves its shape based on it’s viscosity.The viscosity will also control how your simulation absorbs other objects. Try and keep in mind where and how your lava is erupting. As well as how it should interact with your volcano geometry, and surrounding debris and smoke sims.
Here are some parameters you can start with for your FLIP fluid simulation:
- Particle Separation 0.045
- Voxel Scale 0.5
- Influence Scale 7.5
- Droplet Scale 0.025
When rendering, you don’t want your lava to appear as water, or too shiny. So you will have to use displacement maps in your shaders to create the natural bumps of lava. For shading lava you can use a Point VOP to map the temperature from a Pyro VOP. Then can generate better colors.
Make sure the particle separation of your fluid is decreased enough so it doesn’t separate like water as well. Consider playing with the voxel density as well.
For lighting you can also use geometry lights to create an orange and red glow around your lava mesh
One cool thing about Houdini is that it has an Emit Lava Shelf Tool. This creates a preset lava simulation for you at the click of a button. It also applies a lava shader for you to use. It is great for volcanic eruptions and lava streams.
Here are some tips and tricks for operating it:
- Inside your lava FLIP setup you can turn on the Enable temperature Diffusion Parameter on your DOP network. This will enable heat attributes on parts of the lava, and cause cooler parts of the system to heat up and melt.
- You can control the radius of the temperature field with the radius parameter as well.
- The heat and cold bais will control how much the temperature is affected by the temperatures around it.
- The Solidify Threshold Parameter on the Gas Temperature Update DOP will control when the lava will solidify. This will simulate the crust on the lava to form.
- Remember to mind your collisions. In theory, it seems pretty simple to shoot lava and other liquids out of the interior of a mountain. But in this process you might lose particles in the process, or they might become stuck inside your collision object. Double check how your object is being handled as a static object inside your DOP net. Or feel free to check out my collision notes in Houdini here: https://www.katexagoraris.com/troubleshooting-collisions-in-houdi