Disney’s Moana – Lava vs. Water

Disney’s recent release ‘Moana’ is not only a great family film but is also a superb film for its geology. Throughout the film geological formations create stunning backdrops, which are pretty accurate in terms of their geological nature. Not only does the film contain some wonderfully animated geological back-drops but also the tale of a lava monster which cannot enter the sea. In terms of real life volcanology how accurate are the tales and imaginings in this film? In this post I’m going to give some insights into the reality of lava vs water and the geological phenomenons shown in Disney’s latest animation.

An island of ancient lava

The island landscape of the film has as similar appearance to that of the Polynesian, or Hawaiian islands within the Pacific Ocean, with sharp jagged mountain peaks and glistening blue waters. At the beginning of the film the geology of Moana’s home island is alluded to with the presence of black lava on the beach. This lava appears to be thin and has an intricately folded ropy surface – this is thin pahoehoe lava. The thin nature of the lava could suggest that this was the leading edge of a lava flow which then froze when its supply of lava, or the source eruption, ended. It may also be possible that larger, thicker amounts of lava are present beneath the white sandy beaches that surround it on this imaginary shore.

Following many years of tradition on the island, the chief places a flat hexagonal rock onto a pile when they begin their ruling. These hexagonal disks of rock are typically found around areas of columnar jointed lavas which have been weathered on the surface of the earth for many years (even many hundreds or thousands of years). The original columns form as a thick lava cools and contracts (columns can also form in dykes and sills). The presence of these special rocks in the film suggests the presence of ancient igneous activity on the island.

Giants causeway
Columnar jointed lava forming hexagonal columns and plates, Giants Causeway, Northern Ireland. Credit: Mayer 2003

Later in the film thick units of these columnar jointed rocks are accurately depicted as huge towering columns like those seen at Devils Tower National Monument in the USA. There has been a lot of debate regarding how the large columns of the Devils Tower formed, with some suggesting that aliens are responsible for these formations! However, columnar jointing like this can be found all over the world, from Scotland to Hawaii, and it is a natural phenomenon that can be explained by the natural contraction of a lava or magma during cooling. Some mysteries still can’t be fully explained, like how such great thicknesses of molten rock can form perfect columns that are several hundreds of meters in length.

Devils Tower National Monument
Devils Tower National Monument made from columnar jointed igneous rocks, USA. Credit: Faulkingham 2003

Lava vs. water

A major part of the film involves a terrifying lava witch which sits in the sea on a small lava covered reef. When Moana comes face to face with this monster she can be heard saying that the ‘lava can’t enter the water’. But, how does this compare to real life?

Hawaii is a prime example of a currently active volcano where lava is actively found flowing into the sea. Most of the time this produces little danger as the lava happily flows off the land and into the sea where it cools into lava rocks, with a hiss and some steam. In the film when the lava witch touches the water the lava of her skin steams and rapidly cools forming a shell of solid lava. This really does happen in the real world. When lava cools rapidly (known as quenching) the outer part of the lava solidifies, it may produce steam and some smaller fragments of rock at the same time. The lava beneath this outer layer may still be molten and will be somewhat insulated by the surrounding skin of cooled rock. The lava witch can be seen explosively expelling the hardened outer shell of skin, after touching the water, to reveal more molten rock inside.

lava and surtseyan eruptions
Lava entering the sea (left) and a typical hydrovoclanic eruption from Surtsey with white steam clouds and black cock’s tails (right). Credit: US Navy, Street 2007 & NOAA

The lava witch is surrounded by the sea and only lies on a relatively thin reef of lava, it is therefore likely that if this was a real eruption then it would be a hydrovolcanic eruption. This would involve large amounts of water coming into contact with magma erupting from a vent. In the film the lava witch is surrounded by black billowing clouds of ash, in reality (for a hydrovolcanic eruption) this is more likely to contain larger amounts of white steam and less black ash than is portrayed. This is because large amounts of water are likely to be involved in the eruption, more so than the amount of ash produced. An exception to this would be if the erupting vent was completely isolated from coming into contact with sea water in which case only a highly explosive eruption would be likely to produce the large billowing clouds of black ash in this way. During hydrovolcanic eruptions the eruption clouds produced often contain episodic black (ash rich) ‘cock’s tails’ rather than continuous billowing black clouds full of ash.

Would a lava monster in the form of a lava flow exist in this situation in reality? The interaction between the lava and water in a hydrovolcanic eruption is typically highly explosive with no actual lava flows produced, unless, the vent was isolated and interactions with sea water had ceased. Therefore the lava witch probably would not exist in this setting until the vent was been sealed off from the sea and the lava was protected and able to flow from the vent.

Conclusion

To wrap up this post delving into the reality of the animated geology of Disney’s film ‘Moana’ it can be said that the geology is very well portrayed. And you can actually learn a few things about volcanology even from an imaginary lava witch!

7. Staring into Hell

The first time you stare into the belly of an active volcano is a moment that you never forget. In May 2016 I was given the opportunity to join some dear friends in Nicaragua, an amazing country with a large density of active volcanoes. As part of our adventures we took a trip up to the summit of Volcan Masaya where we peered down into ‘the gates of hell’.

Our journey began with a tour guide service in the city of Granada where we booked on to a night-time crater tour. Our trip included transport, guide, entry into the volcano park and gas masks just in case the volcano was emitting too many gases. In the end we got all of these things except for a guide, but the whole experience was no less mind-blowing.

We were driven from Granada to the city of Masaya where we joined a long queue which stretched a long way down the dual carriage way. We slowly slowly crept forward and eventually made it to the park entrance where a fee was paid and we were able to continue in our long queue through the park up to a manned road block. It was dark and humid, all around was vegetation and impatient people getting in and out of their cars. Through the trees a starry night sky could be seen, interrupted every now and again by bright flashes of lightning from a distant storm.

We learnt that only a certain number of cars are allowed up to the summit at a time and when it’s your turn you are given a maximum of 15 minutes to park the car, get out, and peer over the edge into the crater below.

It was finally our turn….We slowly drove in convoy with the other qualifying sightseers up towards the summit. We cleared the trees as we entered into a lava field surrounding the volcano. As we approached the summit the clouds above the vent turned a deep red. The silhouette of crucifix appeared on the horizon against the deep red sky with the occasional flashes of lightning from a nearby thunderhead, the air smelling more and more sulfurous as we got closer. It was incredible…

When the car stopped at the summit we jumped out and raced towards the barriers on the craters rim….the sight that met us was unbelievable. Boiling, shifting, bubbling, glowing orange lava with puzzle pieces caused by various regions of cooled lava floating on the molten mass. The hubub of the sightseers around us was pretty loud but if you cupped your ears in the direction of the lava lake you could hear the frothing and rushing of the bursting, mixing lava below.

You get sucked into a trance by the amazing sights and sounds of the boiling lava and its difficult to pull your self away. Soon though our allotted 15 minutes was over and everyone at the crater was herded back into their cars and told to make their way back down.

There was so much to take in at the craters rim, it wasn’t until afterwards when looking through the images and videos that I had taken that the experience truly sank in. This was an experience that I will never forget. If you happen to be visiting Nicaragua I highly recommend going up to peer into the gates of hell at the summit of Volcan Masaya. Not only for the incredible experience but also because this is one of only a handful of active lava lakes in the world! It’s therefore a very unique experience and I promise that it will be something that you never ever forget.

How fast is lava?

Could you walk away from a lava flow? – recent videos of fast-flowing lava from Kilauea might make you question your walking pace

You should be able to walk away from most lava flows. However, recent videos of the lava flowing from an eruption of Kilauea in Hawaii shows rivers of lava flowing much much faster than this.

The speed of a lava flow is given for the very front of the lava; it’s assumed that once a lava has flowed over an area that no-one will be standing in the middle of a lava flow and therefore the speed there is not as important.

Before you get hot under the collar, the lava in these speedy lava rivers may travel around 60 km/hr (~ 40 mph), but the lava at the very front of the flow will travel only a few km or miles per hour.

However, there are exceptions. For example, lava flows from Nyiragongo, Africa, can travel at 60 km/hr (~40 mph) even at their very front. These lava flows are extremely dangerous as no-one can walk, or even run, fast enough to escape these.

The wonder of pillow lava

Recently huge accumulations of pillow lava have been viewed by NOAA’s Okeanos Explorer in the deep sea off the coast of the American Samoa (w/c 3rd April 2017). The words ‘pillow’ and ‘lava’ don’t seem to make for a comfortable combination, so what is pillow lava, how does it form and what does it look like in the rock record? This article aims to give some insight into the formation of pillow lava with some images of beautifully preserved pillow lava that I recently visited in Oamaru, New Zealand.

What is pillow lava?

Pillow lava is lava that was squeezed out under water to form blobs and pillow-like structures on the sea floor, or at the bottom of lakes. They may also potentially form when lava is extruded beneath ice sheets and glaciers.

The outer layer of the lava quickly cools when it comes into contact with water forming a chilled rim to the pillow. This chilled rim may appear a different colour to the rest of the pillow (for example the black outline of the pillow in the image above), or they may simply be composed of much finer crystals or glass.

In water volcanic glass rapidly becomes altered and decomposes, a process known as devitrification. Therefore many pillow lavas are surrounded by a rim of devitrified material that originally formed a rind of glass.

The centre of the pillow will cool the slowest so may be dense or contain larger crystals, with crystals getting smaller towards the rim. The presence of gas bubbles (preserved as vesicles) may increase towards the rim of the pillow, and some of these may be elongated and stretched into small tubes.

When a lava is extruded into a watery environment the water will be heated and hot water and minerals will circulate through the pillow lavas and any surrounding sediments. These warm fluids can contain dissolved minerals which often precipitate into the vesicles (gas voids) formed in the lava, when this happens the mineral-filled vesicles become known as amygdales.

Thick piles of pillows

Stacks of pillow lava can be seen all over the world preserved within the rock record, from Wales (UK), to the American Samoa, and right the way round to Oamaru, New Zealand.

Pillow lava cross section NZ
Pillow lavas in cross-section in Oamaru, NZ. Credit: S.Wanmer 2017

Pillow lavas aren’t just found in the rock record though, in several locations around the world they can be observed right now forming at the bottom of the ocean!

Links:

https://www.pmel.noaa.gov/eoi/nemo/explorer/concepts/pillows.html – Information, pictures and videos of pillow lava formation provided by NOAA

https://oceanexplorer.noaa.gov/okeanos/welcome.html – Keep up to date with the progress and finding of NOAA’s Okeanos Explorer expeditions

https://volcanoes.usgs.gov/vsc/glossary/pillow_lava.html – Definition of pillow lava and gifs produced by the USGS