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.

 
 
 
 

What does the Greater Manchester Spatial Plan mean for the region’s housing supply and green belt?

Manchester. Image: Getty.

We’re not even halfway through January and we’ve already seen one of the biggest urban stories of the year – the release of Greater Manchester’s new spatial plan for the city-region. The Greater Manchester Spatial Framework (GMSF) sets an ambitious target to build more than 200,000 homes over the next 18 years.

Despite previous statements indicating greenbelt development was off the table, the plan allows for some moderate easing of greenbelt, combined with denser city centre development. This is sensible, pragmatic and to be welcomed but a question remains: will it be enough to keep Manchester affordable over the long-term?

First, some history on Manchester’s housing strategy: This is not the first iteration of the controversial GMSF. The first draft was released by Greater Manchester’s council leaders back in October 2016 (before Andy Burnham was in post), and aimed to build 227,000 houses by 2037. Originally, it proposed releasing 8.2 per cent of the green belt to provide land for housing. Many campaigners opposed this, and the newly elected mayor, Andy Burnham, sent the plan back to the drawing board in 2017.

The latest draft published this week contains two important changes. First, it releases slightly less greenbelt land than the original plan, 4.1 per cent of the total, but more than Andy Burnham previously indicated he would. Second, while the latest document is still ambitious, it plans for 26,000 fewer homes over the same period than the original.

To build up or to build out?

In many cities, the housing supply challenge is often painted as a battle-ground between building high-density homes in the city centre or encroaching on the green belt. Greater Manchester is fortunate in that it lacks the density of cities such as London – suggesting less of a confrontation between people who what to build up and people who want to build out.

Prioritising building on Greater Manchester’s plentiful high-density city centre brownfield land first is right and will further incentivise investment in public transport to reduce the dependence of the city on cars. It makes the goal in the mayor’s new transport plan of 50 per cent of all journeys in Greater Manchester be made on foot, bikes or public transport by 2040 easier to realise.

However, unlike Greater London’s greenbelt which surrounds the capital, Greater Manchester’s green belt extends deep into the city-region, making development on large amounts of land between already urbanised parts of the city-region more difficult. This limits the options to build more housing in parts of Greater Manchester close to the city centre and transport nodes. The worry is that without medium-term reform to the shape of Manchester’s green belt, it may tighten housing supply in Manchester even more than the green belt already does in places such as London and York. In the future, when looking to undertake moderate development on greenbelt land, the mayor should look to develop in these areas of ‘interior greenbelt’ first.

Greater Manchester’s Green Belt and Local Authority Boundaries, 2019.

Despite the scale of its ambition, the GMSF cannot avoid the sheer size of the green belt forever: it covers 47 per cent of the total metropolitan area. In all likelihood, plans to reduce the size of the green belt by 2 per cent will need to be looked at again once the existing supply of brownfield land runs low – particularly if housing demand over the next 18 years is higher than the GMSF expects, which should be the case if the city region’s economy continues to grow.


An example of a successful political collaboration

The GMSF was a politically pragmatic compromise achieved through the cooperation of the metropolitan councils and the mayoral authority to boost the supply of homes. It happened because Greater Manchester’s mayor has an elected mandate to implement and integrate the GMSF and the new transport plan.

Other cities and the government should learn from this. The other metro mayors currently lacking spatial planning powers, in Tees Valley and the West Midlands, should be gifted Greater Manchester-style planning powers by the government so they too can plan and deliver the housing and transport their city-regions need.

Long-term housing strategies that are both sustainable and achievable need to build both up and out. In the short-term Greater Manchester has achieved this, but in the future, if its economic success is maintained, it will need to be bolder on the green belt than the proposals in the current plan. By 2037 Manchester will not face a trade-off between high-density flats in the city centre or green belt reform – it will need to do both.  If the city region is to avoid the housing problems that bedevil London and other successful cities, policy makers need to be ready for this.

Anthony Breach is an economic analyst at the Centre for Cities, on whose blog this post first appeared.