Lava in Hawai'i is creating new land. It also might kill you

Lava flows from Kīlauea. Image: EPA.

There is something special and awe-inspiring about watching new land form. This is what happened recently in Hawai’i as its Kīlauea volcano erupted. Lava is reaching the ocean and building land while producing spectacular plumes of steam. These eruptions are hugely important for the creation of new land. But they are also dangerous. Where the lava meets the ocean, corrosive acid mist is produced and glass particles are shattered and flung into the air. Volcanic explosions can also hurl lava blocks hundreds of metres and produce waves of scalding hot water.

At Kīlauea, lava is erupting from a line of vents on the volcano’s flanks, and is moving downslope to the edge of the island, where it enters the ocean. This is a process that has been witnessed many times at Hawai’i and other volcanic islands. And it is through many thousands of such eruptions that volcanic islands like Hawai’i form.

The new lava being added to Hawai’i by this latest Kīlauea eruption replaces older land that is being lost by erosion, and so prolongs the island’s lifespan. In contrast, older islands to the north-west have no active volcanoes, so they are being eroded by the ocean and will eventually disappear beneath the waves. The opposite is happening to the south-east of Hawai’i, where an underwater volcano (Lōʻihi Seamount) is building the foundations of what will eventually become the next volcanic island in this area.

How lava gets to the ocean at Hawai’i

The lava erupting from the current Kīlauea vents has a temperature of roughly 1150 degrees °C, and has a journey of between 4.5km and 5.5km to reach the ocean. As this lava moves swiftly in channels, it loses little heat and so it can enter the ocean at a temperature of over 1000 degrees°C.

When lava meets the sea, new land is formed. Image: EPA.

What happens when lava meets the ocean?

We are witnessing one of the most spectacular sights in nature - billowing white plumes of steam (technically water vapour) as hot lava boils seawater. Although these billowing steam clouds appear harmless, they are dangerous because they contain the small glass shards (fragmented lava) and acid mist (from seawater). This acid mist known as “laze” (lava haze) can be hot and corrosive. If anyone goes to near it, they can experience breathing difficulties and irritation of their eyes and skin.

Apart from the laze, the entry of lava into the ocean is usually a gentle process, and when steam is free to expand and move away, there are no violent steam-driven explosions.

But a hidden danger lurks beneath the ocean. The lava entering the sea breaks up into blobs (known as pillows), angular blocks, and smaller fragments of glass that form a steep slope beneath the water. This is called a lava delta.

A newly formed lava delta is an unstable beast, and it can collapse without warning. This can trap water within the hot rock, leading to violent steam-driven explosions that can hurl metre-sized blocks up to 250 metres. Explosions occur because when the water turns to steam it suddenly expands to around 1,700 times its original volume. Waves of scalding water can also injure people who are too close. People have died and been seriously injured during lava delta collapses

So, the ocean entry points where lava and seawater meet are doubly dangerous, and anyone in the area should pay careful attention to official advice on staying away from them.

Pillow Lavas form underneath the ocean. Image: National Oceanic & Atmospheric Adminstration (NOAA).

What more can we learn from these eruptions?

Once lava deltas have cooled and become stable they represent new land. Studies have revealed that lava deltas have distinctive features, and this has enabled volcanologists to recognise lava deltas in older rocks.

Remarkable examples of lava deltas have been discovered near the top of extinct volcanoes (called tuyas) in Iceland and Antarctica. These deltas can only form in water and the only plausible source of this water in this case is melted ice. This means that these volcanoes had melted water-filled holes up to 1.5km deep in ice sheets, which is an astonishing feat. In fact, these lava deltas are the only remaining evidence of long-vanished ice sheets.


The ConversationIt is a privilege to see these incredible scenes of lava meeting the ocean. The ongoing eruptions form part of the natural process that enables beautiful volcano islands like Hawai'i to exist. But the creation of new land here can also bring danger to those who get too close, whether it be collapsing lava deltas or acid mist.

Dave McGarvie, School of Physical Sciences, The Open University and Ian Skilling, Senior Lecturer (Volcanology), The University of South Wales.

This article was originally published on The Conversation. Read the original article.

 
 
 
 

Are London’s cycle lanes literally on the wrong side of the road?

A satisfied user of a London cycle lane shows his appreciation to then-mayor Boris Johnson. Image: Getty.

A couple of months ago, I was cycling to work when the bus in front of me slowed. I peered to one side of it, then the other, and looked over my shoulder before pulling out to overtake – a glance motorbike instructors refer to as “the lifesaver” – only to find another cyclist charging into the space I was about the occupy. “Choose a line!”, screamed my fellow road user, who had obviously mistaken the Walworth Road for Herne Hill Velodrome, as they pedalled frantically past.

After I’d finished fuming – and, obviously, overtaken the Lycra lout in a tiring and unbelievably petty commuter chasse-patate – I began to wonder why I’d been thinking about which side of the bus I was going to overtake.

With the increased popularity of cycling in London, the flow of cycle traffic seems to have changed, becoming more opportunistic. Like many cyclists I now filter either side of the motor traffic, and I think I do it more than I used to. While the cycle superhighways are great – especially where they’re physically separate from the road – they often put cyclists in the position of being faster than the motor traffic and on the wrong side of it. On the CS7 from Collier’s Wood to Kennington, for example, cyclists share the road with motor traffic but are forced by the position of the lane to break the most dangerous taboo of urban cycling – passing up the left-hand side of a lorry.

I have never been able to use a lane like this without feeling like I’m in the wrong place, relative to the traffic. So, why aren’t cycle lanes on the other side of the road?

For one thing, given that Britain drives on the left, it makes sense to arrange traffic so that the fastest vehicles are on the right, so that overtaking happens on the right-hand side of the slower vehicle as happens on dual carriageways and motorways. In central London, the average car speed is 7.4mph, while the tracking app Strava – which, admittedly, is likely to be used by faster cyclists – says the average speed of cyclists in London is just under 14mph. This difference grows in rush hour, when cyclists pour around slow-moving motor vehicles.

Secondly, and most importantly, a cyclist on the right-hand side of the cab of a heavy goods vehicle is more visible to the vehicle’s driver. Lorries comprise five per cent of traffic in London but 45 per cent of cyclist fatalities. Many, if not most, of these occur when a lorry turns left and does not notice that a cyclist is in the large blind spot on the far side of the vehicle from the driver. If cycle lanes were on the right, their occupants would be more visible to vehicles; and cyclists could be physically discouraged from occupying the most dangerous areas around an HGV, such as to the side of the cab at a junction. 


London also has a particular hazard for cyclists who are unlucky enough to be hit by a vehicle, in that many streets have guard rails to protect pedestrians from traffic. Fatal accidents have occurred in which cyclists have been crushed against these rails by vehicles, rather than being thrown onto the pavement. But while some have said this is a reason to remove or not install the rails, there is also strong evidence that they protect pedestrians. Again, a better measure might be to move cycle traffic to the other side of the lane, away from the danger zone.

In other accidents, cyclists on the right-hand side have fallen or been shoved by a vehicle into the path of oncoming traffic. If the first lane of oncoming traffic on the other side of the road was a cycle lane, this might make this scenario less dangerous.

It would remove the problem, too, of the many miles of cycle superhighway that are used as generous new parking spaces by drivers, causing cyclists to weave in and out of traffic. 

A lot of drivers would almost certainly be annoyed by the idea of cyclists sauntering past them in what they might consider to be their fast lane. But let’s face it: those people are going to be annoyed by any cyclist, or indeed anything, they see on their journey because they’re in a car, in London, perhaps listening to LBC, which is enough to ruin anyone’s day.

And this, too, might be a reason to put cyclists on the right. The psychologist Tom Stafford has suggested that drivers see cyclists as “free riders” in the traffic system, because they don’t follow the same rules as cars – even if they’re generally aware that they’re following the rules of the road. Dr Rachel Aldred, Reader in Transport at the University of Westminster, has said that cycling is seen by drivers as “playing in the street, and getting in the way of the traffic”. One way to overcome these psychological barriers to accepting cyclists on London’s streets might be to give them a less subjugated position on the road.