Category Archives: Groundwater – geofluids

Erupting mud volcanoes; We have ignition

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Mud
It supports geological processes.
It flows, subsides, and leads to failure, sometimes catastrophically.
It can be beneficial, forming fertile river floodplains.
It can be a pain in the neck, clogging infrastructure.
It oozes when soft; dries brick-hard
People bathe in it. Pigs love it.

And it erupts, as volcanoes.

Not the magmatic kind, with 1000oC lavas or explosive ash columns, but eruptions nonetheless. Most mud volcanoes are much smaller than their magmatic counterparts; some only a metre high, others 10s of metres. Eruptions may be the quiet, oozy kind where mud flows, slithers and slides down slope, or more violent, shooting sticky stuff 10s of metres into the air (or water); some even ignite in a cascade of fireballs. And yes, they do form on the sea floor.  One example in 2015 along the Sea of Azov coast (land-locked between Russia and Ukraine), sent mud and water several metres into the air; you can see the muddy jetsam gradually expanding across the sea surface.  Continue reading

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Nitrate in excess; a burgeoning, global contamination problem

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A “Nitrate timebomb”.  Last week’s media metaphor (Nov 10, 2017), was no doubt intended to create visions of dire deeds. After all, it seems that explosions are not in short supply these days. The actual story though is more droll, based as it is on the slow leakage of excess chemicals called nitrates, into the global environment. No fireworks; only leakage. The headline in several media outlets, only lasted a day or two, barely scratching our collective consciousness. Perhaps the problem is too big, or too remote – a candidate for the too-hard-basket. As Mark Twain might have said, “I guess so, I dunno”.

Nitrogen itself is not a concern; every breath we take contains 80% N2. It’s what we do with nitrogen that is causing problems, particularly in natural systems like soils, surface waters, groundwater aquifers, and ultimately, the oceans. The scientific paper that caused these brief media conniptions was published this month in Nature Communications (it is Open Access). Continue reading

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Springs and seeps

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It rains quite a bit on Mamaku Plateau, the tableland underlain by volcanic debris that was  deposited violently 240,000 years ago; an eruption that also gave rise to the Lake Rotorua caldera (central North Island, New Zealand). Some of that rain seeps into the myriad fractures, nooks and crannies, and heads west as groundwater. Fifty to 100 years later, that same water emerges, chilled (a cool 11oC), at Blue Springs (about 40km west of Rotorua). Spring water here flows at 42 cubic metres per minute (9,240 gallons per minute), enough to maintain a decent-sized stream (Waihou Stream). Continue reading

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The brutality of Surtsey’s laboratory

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I recently came across a local newspaper article describing a new volcanic island, rising from its own ashes above the sea floor, off the coast of Tonga.  The subtlety of memory returned me to 1963, and an announcement over our morning radio, of the birth… of a volcanic island off the coast of Iceland. Images, arriving a couple of days later (this was 1963 after all), gave witness to a natural brutality I had not seen before; the sea in boiling turmoil, torn by erupting columns of rock and steam. Beautiful, in an awe-filled way.

It has been fifty years since the cessation of volcanic activity. Surtsey has become home to plants and birds, a laboratory for the adaptable, the dispersible, and the colonial.  The only sounds that resonate now are noisy gulls and pounding North Atlantic waves. Continue reading

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Contrails, analogues, and visualizing groundwater flow

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Analogues and analogies.  Standard dictionaries define these as a comparison, correspondence, or similarity between one thing and another, that can apply to concepts, ideas or physical entities. They are tools, used to illustrate concepts, particularly abstract ideas, to help explain phenomena or theories. Science makes frequent use of analogies. It does so because many phenomena that it attempts to investigate and explain, extend beyond normal human experience, beyond what is visible to the unaided eye, beyond what we can touch.  Well-chosen analogies can help us understand the universe without, and the universe within. Continue reading

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A misspent youth serves to illustrate groundwater flow

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Groundwater is always on the move. Under some conditions, in fractures or other large conduits, it can move quickly; almost at a walking pace. Under other conditions it moves inexorably slowly, like fractions of a millimeter a year. Regardless, it is always compelled to move. Movement requires energy.  Where does this energy come from?  What drives the flow of groundwater?  Answers to these questions provide the foundations to the science of hydrogeology. Continue reading

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Stabilisation of an architectural icon; the Leaning Tower of Pisa

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Sunday in Pisa proved to be a welcome change from the usual tourist-cramped, shoulder-barging throngs of popular attractions in Tuscany.  No problem finding a seat in a decent café, en route to the Piazza del Miricoli.  Cross the street, turn a corner and there – the massive, white-marbled Pisa Duomo, Romanesque grandeur with a veneer of 21st Century scaffolding.  But the sense of balance normally attributed to cathedrals, is disrupted by the stand-alone bell tower that leans precariously, like a drunk looking for a lamppost.  The Leaning Tower of Pisa has been looking for a lamp-post for almost one thousand years.  And for a thousand years, people have been drawn to the tower not because it is particularly beautiful, but because it looks like it is about to fall over. Continue reading

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