An island apart

by Lindsey Atkinson

Having recently had the good fortune to visit Barbados and some of the Windward Islands in the Lesser Antilles I was struck by the difference between Barbados and the other islands and curious to find out why.  Now you’ll have to excuse me as I am not a geologist so I am wandering into new territory with this blog...

The Windward Islands are the more southerly islands of the Lesser Antilles, including  Martinique, St Lucia, St Vincent and the Grenadines, and Grenada.  They lie near the eastern edge of the Caribbean tectonic plate and are part of the Lesser Antilles volcanic arc.  Being largely volcanic in origin the larger islands are mountainous with a rich volcanic soil and they still have active volcanoes.  Seismic activity in the area is monitored by the University of the West Indies Seismic Research Centre.  

Sulphur springs, La Soufrière, St Lucia

Sulphur springs in La Soufrière, give away St Lucia’s volcanic origins while its namesake, La Soufrière (1234m) on St Vincent, last erupted in 1979 replacing the lake that used to lie in the crater with a lava dome.



Inside the crater, La Soufrière, St Vincent

Barbados stands apart from the other islands being the most easterly of the Caribbean islands, 160km east of St Lucia.  It also differs in being a relatively low lying island, with the highest point at Mount Hillaby (340m), and it differs in origin from its nearest neighbours.


Former coral colonies, Little Bay



Sedimentary layers, Little Bay

Unlike the Windward Islands, Barbados was not formed by volcanic action and it lies at the very edge of the Caribbean tectonic plate.  As the South American plate was subducted under the Caribbean plate sediment was scraped off the South American plate, including deposits of pelagic organisms, forming an accretionary prism.  These layers were subsequently covered by a coral cap.  Both former coral colonies and sedimentary layers  can be seen exposed on the east coast, as here at Little Bay (left).

The movement of the plates resulted in uplifting of these deposits until eventually the island was exposed above sea level.  This happened in stages resulting in ridges which are visible across the island.

Harrison Caves

Little Bay

The island is therefore predominantly limestone, with little surface water as the water filters through the rock.  Beneath the surface are caves such as Harrison Caves with stalactites and stalagmites while on the surface there are dry gullies.  Some of these gullies may have formed when limestone cracked during uplifting or, as in the case of Welchman Hall Gully, where a cave roof has collapsed.  


Erosion has also done its work as the pounding Atlantic waves on the east coast have resulted in the dramatic cliffs of Little Bay and the limestone ‘mushroom’ rocks  of Cattlewash Beach. 

'Mushroom' rock on Cattlewash Beach

And of course erosion of the coral rocks has created the beautiful sandy beaches so beloved of tourists!

Crane Beach, South Coast



Bibliography:

Barbados National Trust   http://barbadosnationaltrust.org 

Donovan SK and Harper DAT (2005) The geology of Barbados: a field guide.

Caribbean Journal of Earth Science 38: 21-33.

Radtke U and Schellmann G (2006) Uplift History along the Clermont Nose Traverse on the West Coast of Barbados during the Last 500,000 Years - Implications for Paleo-Sea Level Reconstructions. Journal of Coastal Research 22: 350-356

Saunders et al. (1984) Stratigraphy of the Late Middle Eocene to Early Oligocene in the Bath Cliff Section, Barbados, West Indies.  Micropaleontology 30: 390-425

The Soufrière Foundation http://www.soufrierefoundation.org/about-soufriere/geology

University of the West Indies Seismic Research Centre http://www.uwiseismic.com/Default.aspx

'Paradise tax': the price Hawaiians are prepared to pay for living near volcanoes

This week we have a guest blog by Jazmin, a PhD student in the Department of Geography, Environment and Earth Sciences at Hull. She is interested in the links between social, cultural and physical mitigation construct factors to the adaptation of volcanic risks.

By Jazmin Scarlett, University of Hull

The destruction caused by the lava of Kilauea are grabbing the attention of the international media. Last week, footage showed this eruption claiming its first house in Pahoa and people began to question whether to try to halt the flow of lava and how you might go about it.
But the daughter of the family’s home that was destroyed was remarkably sanguine about losing the family home:

If you’re going to live on a volcano, it’s about her (the Hawaiian Goddess Pele), not us … if she wants her land back, then get out of the way. I like to call it ‘paradise tax’.

The volcano is part of their culture. Pele is such a dominant force in Hawaiian’s lives they tend to accept the possibility that it might erupt. For a lot of Hawaiians, their respect for the volcano god appears to override their fear of eruptions.

For instance, the now-displaced family is building another home on older, solidified lava. Hawaii is entirely volcanic due to being situated on a hot spot resulting in a continual output of volcanic material. As far as I am aware, the family did not have insurance. This shows their ability to bounce back and recover from a hazardous event.

Not everyone responds in the same way. Some people are scared, some panic or remain anxious. And yet Hawaiian people have dealt with Kilauea’s almost continuous eruption for more than 50 years now. Over the course of many generations, they are actively learning about the volcano and the risks it poses.

Hawaii hasn’t lost many lives to the lava of Kilauea – mainly because the lava flows are slow (due to a combination of its properties and the land it flows over) – slow enough, at least, for people to respond in time and adjust to the situation (for example evacuating like the Pahoa family did a month before their home was destroyed) but also because of the combined efforts of the public, the civil defence and government authorities.

To date, Kilauea has destroyed more than 200 properties, many roads and claimed the lives of four people in modern times. Historically, the largest number killed by a Mount Kilauea explosion was in 1790, ranging from 80-400 people, a number still being debated.

Photo: BRUCE OMORI/PARADISE HELICOPTERS

Someone’s got your back

The civil defence teams, with the combined efforts of volcanologists and all those involved in keeping the people safe, have experience in how to deal with and adapt to the ever-evolving situation. A recent update shows a collective calm and professionalism, presenting the information in a way that Hawaiians can comprehend.
The risk of property being destroyed is neither exaggerated nor underestimated. The authorities explain the risk by presenting as much information as available – and Hawaiians tend to trust that the authorities are being realistic. This feeds into how people learn and assess the risk to themselves and their properties.

PHOTO: US GEOLOGICAL SURVEY

Business as usual

At present there appears to be little chance of halting the advancing lava flow. The properties of the lava and external influences, such as the steepness of the terrain, mean that the point at which the lava flow might stop naturally is not yet apparent.

What has been shown in news bulletins are the more runny lava flows that volcanologists call “pāhoehoe” (the “hoe” meaning “to paddle” in Hawaiian) but this is not representative of the reality of the eruption which is producing more viscous, slower moving lava (or “aʻā” as it is known locally). As in Italy and Iceland there have been attempts to stop lava flows in Hawaii but with mixed results. For instance, according to a report in NPR,a US$2m engineering project successfully diverted lava flows near Mount Etna in 1983. But a similar attempt in Hawaii in 1955 and 1960, however, failed because of lack of proper understanding of the situation.

Given the effectiveness of the volcanic hazard management system in place in Hawaii, I have no doubt that such attempts will be made if they are reasonable, through the combined efforts of volcanologists, engineers, the civil defence and a guaranteed investment for the project.
But in case the Hawaiian authorities don’t succeed in halting or diverting the eruption and the flow of lava, we mustn’t underestimate the power of Hawaiian culture and belief to deal with such volcanoes. Living in such parts of the world, disaster resilience is not an urgency but a way of life.

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

Iceland: a geographer’s paradise

By @DrLucyClarke

I recently co-led a 7-day undergraduate field trip to south-western Iceland.  This was my first visit to the country so I was really excited to see the land of fire and ice that I had heard so much about!  One of my motivations for becoming a geographer is my love of the outdoors, thirst for exploration and knowledge of new places and environments, so the field trip element of physical geography has therefore always held a huge appeal for me.  And to date my career has taken me to some amazing places - both within the UK and further afield.  So not surprisingly when I was approached to take part in the student field trip to Iceland, I jumped at the opportunity!

Iceland is a fascinating country - it lies between two continental plates, the Eurasian and the North American, that are constantly pulling away from each other.  The rift valley that this is creating is one of only two places in the world that you can see this happening on the Earth’s surface, the other being the Great Rift Valley of Eastern Africa. You can literally walk between, and next to,  the edge of actual continental plates and on some of the ‘youngest’ crustal surface on the planet.  This geographical rarity alone is reason to visit Iceland but this incredible place has much more has to offer!

Þingvellir: the rift valley in Iceland where the Eurasian and North American continental plates are pulling apart. The photos are showing the edge of the North American plate, with the lower photo looking out over the rift valley towards the Eurasian plate.

Iceland is also located over a hotspot (see the previous blog post by @volcanologist  for more information on hotspots), which is thought to have originally formed the island. This and the rift valley mean that Iceland is tectonically active, as you drive around, the horizon is littered with spectacular volcanoes and relict lava flows are dotted across the landscape.

The volcanic scenery in Iceland: the snow-capped summit of the volcano Hekla, the basalt cliffs at Vik formed from 3 distinct lava flows lying on top of one another, and the lava field from the 1783 Laki eruption (from left to right).

Not only do the volcanoes and related features provide a stunning backdrop, they are of interest to geologists to better understand how and why they erupt and what this means in relation to the inner workings of the Earth.  The rich history of Icelandic volcanic eruptions also provides a fantastic resource for geographers trying to understand the surface processes.  Each eruption deposits a layer of tephra across the ground in affected areas, these are then reburied by subsequent layers of soil through time. The composition, thickness and biota in these layers can tell us a lot about the environmental conditions occurring at the time of deposition (for example we can use the pollen as explained by @DrM_Farrell in one of her earlier blog posts).  The date of  these volcanic eruptions is well documented and, as each eruption has a unique signature, we can identify the date of the tephra layers and as such you can constrain the time periods of the other soil layers using a technique called stratigraphy.  This method has been used to better understand the influence that humans have had on the landscape since settlement in the 9^th century, the impact of deforestation and the effect of changing climate on soil formation and erosion.

A soil profile showing the distinctive black tephra layer at the top of the photo.

My main research area is the fluvial environment, so I was really excited to see the amazing braided rivers and waterfalls that Iceland had to offer, and I wasn’t disappointed! The scale of these are far greater than any in the UK and it was amazing to see them.  Below are some photos giving examples of some of the fluvial features we visited. The top row gives some examples from the many impressive waterfalls there are along the southern coast of Iceland. From left to right, these are Gullfoss (translated as Golden Falls), Hjálparfoss (Help Falls) and Skógafoss (Forest Falls). On the bottom row are images of some of the rivers, at either end are examples of braided river systems from the Þórsmörk valley into which the Eyjafjallajökull glacier (sitting on the slopes of the volcano that created havoc to European air space in 2010) drains. The high sediment load in the area creates these fantastic braided channels in the river systems. The middle picture on the bottom row shows the River Skeidará , the different colours represent the merging of water from two different sources, glacially fed water that has a heavy sediment load and fluvial (clearer) water.

As well as flowing water, as you can imagine Iceland also has plenty of frozen water and there are numerous glaciers and ice caps. The northerly location of Iceland -65° latitude mean that winters are cold and dark.   These cold conditions promote glacier formation.  On the field trip we investigated the geomorphological evidence for the retreat of the Skaftafell glacier which included a hike on the glacier ice of the Sólheimajökull glacier to measure the impact of debris cover on the glacier surface.  It was a great thrill for the students to get up close and personal with a real glacier.

Looking up the Skaftafell glacier from its terminus (left image), the glacier walk on the Sólheimajökull glacier (2 right hand images).

Field trips typically consist of long days in the field followed by long nights analysing the data with the students, so although the trip was hard work it certainly didn’t in any way detract from the awe of the place.  Iceland presents a fantastic opportunity to investigate a variety of geological and geographical processes and landforms, and experience incredible scenery.  As an added bonus I was also treated to my first ever viewing of the Northern Lights, as well an Arctic fox up close!

Arctic Fox

So overall I found my field trip to Iceland both exhilarating and exhausting, and I would wholeheartedly recommend Iceland as well worth a visit for anyone.  I’m certainly planning to go back for my own research so watch this space for updates…