This week, I thought I’d do some in-depth examination of some very deep subjects.  Keep reading, you’ll see what I mean!

My first item is an update on a subject we’ve covered several times on The Deep.  I’m sure you all remember Lusi.

THE ROOT CAUSE

On May 29, 2006, a volcano erupted on the island of East Java in Indonesia.  But it turned out this was no ordinary volcano spewing hot lava nor was it coming from a lofty volcano mountain.  This volcano pumps out hot mud that doesn’t mound up to form a hill but has since spread out to cover several square miles.  The volcano was called Lusi and in the two and a half years of its eruption, it has swamped 12 villages and displaced 30,000 people from their homes.  Lusi is still flowing today at 3.5 million cubic feet per day, enough to fill 53 Olympic swimming pools.

Well, hey, when you live in the Ring of Fire, you have to expect volcanoes and earthquakes and other consequences and if you don’t like it, you should move somewhere else.  There’s just one little glitch in this scenario.  A group of petroleum geologists meeting at Cape Town, South Africa has concluded that Lusi is not a ‘natural’ volcano.  She’s man-made.

The 74 scientists considered the evidence presented by four experts in the field and then voted on two scenarios.  Forty-two scientists voted that Lusi was triggered when Lapindo Brantas, an Indonesian oil company drilled the gas exploration well called Banjar-Panji-1.  Only 3 scientists voted for the alternative explanation.  This hypothesis stated that Luisi’s eruption was triggered by an earthquake that occurred two days earlier with an epicenter located 175 miles from Lusi.  Sixteen scientists voted that the evidence was inconclusive and 13 said that a combination of earthquake and drilling were the cause.

There was some pretty strong evidence that the drilling triggered Lusi.  The key points presented to support the drilling hypothesis were:

• the earthquake was too small and too far away to have been the trigger.
  
  
• the well was being drilled when Lusi erupted and is only 500 feet from the volcano site.
  
  
• large amounts of water were pumped into the well the day before the eruption, resulting in pressures the sides of the well couldn’t tolerate.
  
  
• the pressure measured in the well after the influx provides strong evidence that the well was leaking and even evidence for the initial eruption at the surface.

One of the speakers, leading geologist Professor Richard Davies of Durham University, UK, commented: "The conference allowed us to present new data on the pressures in the well the day before the eruption and these provide a compelling tape recording of the well as it started to leak.  We were particularly grateful to Lapindo, the company involved in the drilling, who were widely applauded at the meeting for their willingness to take part in the discussion."

Prof Davies added: "I remain convinced that drilling was the cause of the mud volcano. The opinion of the international scientists at the event in South Africa adds further weight to my conviction and the conclusions of many other leading scientists who have studied Lusi."

Susila Lusiaga a drilling engineer and part of the Indonesian police investigation team said: "There is no question, the pressures in the well went way beyond what it could tolerate – and it triggered the mud volcano."
Michael Manga, Professor of Earth and Planetary Science at the University of California, Berkeley, said: "The key observation from an earthquake perspective is that there were many much larger and quite a bit closer earthquakes that did not trigger an eruption.  The Yogyakarta earthquake was simply too small and too far away to initiate an eruption."

But wait!  There’s even better news.  It turns out that Lusi isn’t a volcano after all.

Recent research undertaken by scientists at Durham University UK, and the Institute of Technology Bandung in Indonesia, showed Lusi is collapsing about 45 feet per year, punctuated by 10 foot collapses.  At this rate, Lusi’s ‘cone’ could subside to a depth of more than 500 feet.  Oh boy, just what Indonesia needs, an upside down volcano!

The main vent of the Lusi mud volcano taken within a few months of eruption. (Credit: Durham University)

Lusi may be deep, but now we’re going to journey to the Atlantic Ocean and go a little deeper!

COLD WATER CORAL

One of the first things you learn about coral reefs is that they grow only in the tropics.  If you travel away from that deliciously warm water, the corals vanish.  So imagine the surprise of some research scientists when they traveled almost 3,000 feet below the surface of the Atlantic Ocean and discovered coral reefs growing on the bottom!

Furu Mienis, a Dutch scientist has discovered several hills on the ocean floor that are covered with these unknown cold-water relatives of the better-known tropical corals.

Dr Mienis studied the development these cold-water corals at depths of 1,000-3,000 feet. The reefs are located along the eastern continental slope from Morocco to Norway, on the Mid-Atlantic Ridge and on the western continental slope along the east coast of Canada and the United States.  Mienis studied the area to the west of Ireland along the edges of the Rockall Trough.

Cold-water corals are mainly found on the tops of carbonate mounds in areas of high current because of strong internal waves.  These waves are caused by tidal currents and lead to an increase in local turbulence that results in the seawater being strongly mixed in a vertical direction.  These vertical currents create a ‘food highway’ between the nutrient-rich, sunlit zone at the sea surface and the dark depths.  This allows these cold-water corals to feed on algae and zooplankton that live in the upper layers of the sea.

Climate change has exerted a considerable influence on the growth of corals and the development of carbonate mounds.  For example, corals stopped growing during ice ages.  Present-day global warming and the resulting acidification of the oceans also pose a threat: organisms are less effective at taking up carbonate from seawater that is too acidic.  This is true not only for corals but also for some species of algae that are a source of food for the corals.  Other activities on the seabed that can cause damage to the coral reefs are offshore industries and bottom trawlers. A number of European areas containing cold-water coral reefs have already obtained protected status.

Example of the cold-water corals being studied in the Atlantic Ocean at depths of six hundred to a thousand metres. (Credit: Marc Lavalije, NIOZ)

Corals in the deep sea.  My guess is that they need to rewrite some textbooks!

And for our last article, we’re going to go REALLY deep; probably as deep as it’s possible to get.

MOUNTAIN CLIMBING FROM ABOVE

Scientists from Durham University are using robots to explore the depths of the Atlantic Ocean.  They hope to study the growth of underwater volcanoes that build the Earth's crust.  During their five-week expedition they’ll use explorer robots to map individual volcanoes on the Mid-Atlantic Ridge tectonic plate boundary, the mountain range that runs down the center of the Atlantic Ocean.  Even though this is a mountain range their tops are almost two miles below the surface of the sea.

They’ll use another robot called ISIS, to collect rock samples from the volcanoes.  These rocks will be dated using various techniques to shed more light on the timescales behind the growth of the Earth's crust and the related tectonic plates.

As tectonic plates -- formations that make up the Earth's shell - are pulled apart by forces in the Earth, rocks deep down in the mantle are pulled up to fill the gap left behind.  As the rocks rise they start to melt and form thousands of volcanoes on the sea floor, which eventually cluster into giant ridges.  The Mid-Atlantic Ridge plate boundary contain hundreds of individual volcanoes that are roughly 1000 ft tall.

Principal investigator Professor Roger Searle, in the Department of Earth Sciences, at Durham University, said: "The problem is that we don't know how fast these volcanoes form or if they all come from melting the same piece of mantle rock.

"The ridges may form quickly, perhaps in just 10,000 years (about the time since the end of the last Ice Age) with hundreds of thousands of years inactivity before the next one forms, or they may take half-a-million years to form, the most recent having begun before the rise of modern humans.

"Understanding the processes forming the crust is important, because the whole ocean floor, some 60 per cent of the Earth's surface, has been recycled and re-formed many times over the Earth's history."
The team will date the volcanoes using radiometric dating (which measures the radioactive decay of atoms) and by measuring the changing strength of the Earth's magnetic field through time as recorded by the natural magnetism of the rocks.

Diving the Atlantic Ridge.  Who knows what wonders they will find?  Seventy per cent of our planet is covered with water and we learn about new things found there every single day. 

Cruise on over to the Deep Website at www.thedeepradioshow.com to learn more about . . The Deep! and many other topics.  Enjoy!