Category Archives: Geology

Life below a kilometre of Antarctic ice

Biology, Earth Science, Geology

Did you know life forms have been discovered in a lake nearly a kilometre below Antarctica?

American scientists drilled down to Lake Whillans to retrieve subglacial water samples and detected life forms using RNA sequencing.

Despite temperatures of -0.5°C, oxygen levels 1/7th of surface water and complete darkness, they detected ~4,000 species of bacteria.

They get their energy from chemicals such as iron (FeII) and sulphides.

This further supports the idea that life is extremely tough and can survive virtually anywhere on Earth.

Similar conditions are predicted in the liquid oceans below the ice crusts of Europa and Enceladus, the moons of Jupiter and Saturn, respectively. Therefore, it is possible that life could exist elsewhere in the solar system.

 

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Background

Life appears in many unlikely and inhospitable environments on Earth.

Could it possibly exist in the extremely harsh environment below a kilometre of ice in Antarctica?

There are ~400 lakes below ~55% of Antarctica.

Lake Whillans is 800m below the ice, ~12 x 7 km in size, but only ~2.2m deep.

Materials and Methods

A team of American scientists used a hot water drilling system to bore through 800m of ice to retrieve water samples from Lake Whillans.

They detected life forms in the water using gene sequencing (of small subunit ribosomal RNA).

Results

The water temperature was -0.5°C, pH 8.1, oxygen levels 1/7th of surface water and completely dark (no sunlight).

The source of the water was found to be melting glaciers (heated by geothermal heating and the friction of glaciers grinding over the bedrock), with only a very small amount of sea water.

Incredibly, the water contained ~4,000 species of bacteria (prokaryotes).

No eukaryotes (e.g. worms) were found, although it remains possible they are down there.

The bacteria get their energy from chemical sources. The crushing of rocks by the glaciers releases chemicals such as iron (FeII) and sulphides that react with oxygen in the water to provide the bacteria with energy.

The crushed rocks also release phosphorous, however another essential nutrient for life, nitrogen, is harder to come by. This is mostly supplied by a few species of nitrifying bacteria and recycling from dead bacteria.

Discussion

Bacteria are able to survive in the extremely harsh environment of Lake Whillans in Antarctica below nearly a kilometre of ice in freezing conditions without any sunlight.

Further supports the idea that life is extremely tough and can survive virtually anywhere on Earth.

Similar conditions are predicted in the liquid oceans below the ice crusts of Europa and Enceladus, the moons of Jupiter and Saturn, respectively. Therefore, it is possible that life could exist elsewhere in the solar system.

Article

A microbial ecosystem beneath the West Antarctic ice sheet

Christner et al., 2014 Nature 512:310-3

Keywords

Life, bacteria, prokaryote, eukaryote, survive, microbiology, Antarctica, ice, lake, Lake Whillans, RNA, ribosome, sequencing

Subject

Science, Biology, Earth Science, Geology, ST1-9ES, ST1-11LW, ACSSU211, ST2-8ES, ACSSU075, ST2-11LW, ACSSU073, ST3-11LW, ACSSU094, SC4-15LW, ACSSU112, SC5-14LW, ACSSU176

Low oxygen delayed emergence of animals on Earth

Biology, Earth Science, Geology

Bacteria took ~1 billion years to emerge on Earth, but why did it take another ~3 billion years for animals to appear?

Scientists analysed isotopes of Chromium in rocks as a measure O2 levels in the atmosphere of the early Earth.

Reduced-Cr(III) indicates low O2 levels, oxidised-Cr(IV) indicates high O2 levels.

Atmospheric O2 levels dramatically increased ~700-800 million years ago, just before the emergence of animals in the Cambrian explosion.

The rise in O2 levels (and decrease in CO2) was mostly caused by photosynthesis in cyanobacteria (and later algae).

This was a crucial factor for helping animal life emerge on Earth.

 

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Background

The Earth is ~4.54 billion years old.

The first life forms were bacteria, then cyanobacteria (photosynthesising microorganisms), emerging around ~3-3.6 billion years ago.

Multi-cellular animals (metazoans) took much longer to appear, sometime around ~540 million years ago. This period is called the Cambrian explosion (lasting ~25 million years), when many new animal species emerged (e.g. sponges, molluscs, crustaceans, worms).

If unicellular life took ~1 billion years to emerge, why did it take another ~3 billion years for animals to appear?

Materials and Methods

A team of scientists (including Peter McGoldrick from the University of Tasmania) measured oxygen levels in the early Earth’s atmosphere by analysing isotopes of Chromium found in rocks of different ages from Australia, China and North America. High levels of reduced Cr(III) indicate low atmospheric oxygen levels, while higher levels of oxidised Cr(IV) indicates high atmospheric oxygen levels.

Results

Early Earth atmosphere had very low O2 levels (high CO2 levels).

Atmospheric O2 levels dramatically increased ~700-800 million years ago, just before the emergence of animals in the Cambrian explosion.

Discussion

The rise in atmospheric O2 levels was a crucial factor for helping animal life emerge on Earth.

The rise in O2 levels (and decrease in CO2) was mostly caused by photosynthesis in cyanobacteria (and algae).

Genetic and developmental innovations almost certainly contributed to emergence of animals as well.

Article

Low mid-proterozoic atmospheric oxygen levels and the delayed rise of animals

Planavsky et al., 2014 Science 346:635-8

Keywords

Life, Earth, bacteria, cyanobacteria, photosynthesis, oxygen, O2, CO2, carbon dioxide, atmosphere, Cambrian, animal, chromium, isotope, reduced, oxidised, rocks

Subject

Science, chemistry, ST1-11LW, ACSSU211, ST2-10LW, ACSSU044, ST3-11LW, ACSSU094, SC4-12ES, ACSSU153, ACSSU115, SC4-14LW, ACSSU111, ACSSU149, ACSSU150, SC5-13ES, ACSSU189, SC5-14LW, ACSSU175, SC5-15LW, ACSSU185, SC5-17CW, ACSSU178, ACSSU179

Why is gold valuable?

Chemistry, Earth Science, Geology

Of all the elements and compounds in the world, why has gold been a major form of currency throughout history?

The answer is in its chemistry.

It is a stable, non-reactive substance suitable for long-term storage.

Since it is an element, it can’t be destroyed.

It is highly malleable for shaping into coins and jewellery. Also non-toxic, so it can be worn.

Nearly all of it arrived from asteroids, so it is rare and there is a finite amount on Earth, making it ideal for trading.

It is consistent, since there is only one type of pure gold. Therefore, everyone’s gold has the same value.

Biggest nugget ever discovered was the Welcome Stranger nugget found 3 cm below ground near Dunolly in central Victoria in 1869. It was 61 x 31 cm and weighed 110 kg.

After thousands of years, gold is still being used as an important form of currency (currently used to hedge against the value of the dollar).

 

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Gold is rare and shiny, therefore highly sought after.

Gold is a highly malleable metal and can be moulded into virtually any shape desired. Thus, it could be moulded into portable forms of currency, such as coins and jewellery.

It is non-toxic and non-irritating, also making it suitable for carrying coins and jewellery.

It is one of the most stable elements. It doesn’t react with air or water, therefore doesn’t rust, dissolve or lose its shiny lustre. Makes it a suitable long-term store of value.

Since it is an element, it can’t be destroyed. Theoretically, it can be recovered from anything.

There is a finite amount on Earth, about enough to fill a tennis court to a height of ~10 metres. Therefore, there is a set amount of currency that can be traded (can’t make your own gold).

It is consistent. Because it is an element, there is only one type of pure gold. Therefore, everyone’s gold is the same and has the same value. Unlike other precious substances (e.g. diamonds) that can vary in quality (therefore value).

Nearly all gold on Earth arrived from asteroids.

Biggest nugget ever discovered was the Welcome Stranger nugget found 3 cm below the ground near Dunolly in central Victoria in 1869. It was 61 x 31 cm and weighed 110 kg.

Article

Simon Evans goes to market: Gold. BBC 4 radio program, June 2, 2014. With guests Tim Harford, Merryn Somerset Webb and Dominic Frisby.

Keywords

Gold, element, substance, chemical, compound, currency, money, value, economics, periodic table, metal

Subject

Science, chemistry, ST1-13MW, ST2-13MW, ACSSU074, ST3-13MW, SC4-16CW, ACSSU152, SC5-16CW, ACSSU186

Isolation helps, not hinders coral reefs

Biology, Earth Science, Geology

Coral reefs are under increasing threat by human development, pollution and rising ocean temperatures.

It was assumed that isolated reefs were most vulnerable, because following damage, recovery involves migration of species from nearby reefs to recolonise and rebuild them.

For isolated reefs, this would be slower or not occur at all.

Here they studied the recovery of the isolated Scott reefs off Western Australia, which were badly bleached by hot weather in 1998.

They found that the reef system had rapidly recovered within 12 years.

It might have been even more pronounced if it wasn’t for 2 cyclones, a disease outbreak and another bleaching.

This suggests that isolation is not a disadvantage for coral reefs.

In fact, they benefit from being a long way from their most serious threat – humans.

 

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Background

Coral reefs are under increasing threat by human development, pollution and rising ocean temperatures.

What is the best way to protect them?

It was assumed that isolated reefs were most vulnerable, because following damage (e.g. cyclone), recovery involves migration of species from nearby reefs to recolonise and rebuild them. For isolated reefs, this would be slower or not occur at all.

Here they investigated this question using a damaged coral reef off the coast of WA.

Materials and Methods

The Scott system of reefs is 250 km off the coast of WA in the Indian Ocean. It is also 250 km away from the nearest reef and 1000 km from the nearest large city. There is very little fishing or other human pressures. Extreme water temperatures caused bleaching in 1998, killing up to 90% of the corals. Recovery of the reef was monitored over the next 12 years.

Results

Following bleaching damage to the reef in 1998, there was a surprisingly rapid recovery.

Within 12 years, the coral cover increased from 9% to 44%.

This was not due to migration of corals from other reefs (too isolated). Rather, the recovery was driven by the growth of remnant corals that survived the bleaching.

The recovery might have been even more pronounced if it wasn’t for 2 cyclones, a disease outbreak and a second bleaching within the 12-year recovery period.

Discussion

Isolation was not a disadvantage for coral reefs.

This is good news for coral protection, since following damage they can quickly recover (at least quicker than previously thought).

In fact, the isolation seems to be an advantage, since they are further away from interference, especially from humans.

Article

Recovery of an isolated coral reef system following severe disturbance

Gilmour et al., 2013 Science 340:69-71

Keywords

Ecosystem, ecology, biodiversity, coral, reef, ocean, Australia, bleaching, recovery

Subject

Science, geography, biology, ST1-10LW, ACSSU030, ST1-11LW, ACSSU211, ST2-8ES, ACSSU075, ST2-11LW, ACSSU073, ST3-11LW, ACSSU094, SC4-13ES, ACSSU222, SC4-15LW, ACSSU112, SC5-13ES, ACSSU189, SC5-14LW, ACSSU176

‘Oceans’ of water deep inside the Earth

Earth Science, Geology

Where did all the water in the Earth’s oceans come from?

One theory is it came from ice comets crashing into the Earth.

However, scientists have discovered that a diamond from Brazil that was that formed deep inside the Earth’s mantle (410-660 km) contains a rare mineral called ringwoodite.

This ringwoodite contains a relatively large amount of water.

Since the mantle is so big and contains quite a lot of ringwoodite, this means there could be huge amounts of water down there.

Therefore, the water in our oceans could have come from deep inside the Earth and not from comets.

That is, the water was mixed in with the rocks when the Earth was originally formed, and some of it is still down there.

Future isotopic analysis of water from the oceans, mantle and comets could sort this out conclusively.

 

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Background

Where did all the water in the Earth’s oceans come from?

One theory is it came from ice comets crashing into the Earth.

Another theory is it mixed with the rocks when the Earth first formed, and some of it still remains inside the Earth.

The crust is very thin (5-30 km thick).

Below that, the mantle is ~3,000 km thick.

Within the mantle is a layer called the transition zone at depths between 410-660 km.

Very little is known about the transition zone because samples from this region are extremely rare.

Materials and Methods

Diamond Juc29 from the Juina district of Brazil is 5mm across and weighs 0.09g. Scientists from Canada analysed its chemical composition using various forms of spectroscopy (X-ray diffraction, Raman, infrared).

Results

The diamond was formed in the transition zone (410-660 km) under huge pressures (>15GPa) and high temperatures.

Inside the diamond they discovered a tiny speck (0.04 mm across) called ringwoodite.

This mineral (MgSiO4) is only formed by ultra-high pressures at great depths. It is common in the mantle, but rarely seen at the surface because it is destroyed at lower pressures.

Since ringwoodite is present in the diamond, it means that the diamond must have reached the surface very quickly (e.g. volcanic eruption).

Importantly, the ringwoodite contains a relatively high amount of water.

Discussion

Considering the large amount of ringwoodite and related minerals (olivine, wadsleyite) in the mantle, this means there could be a lot of water down there, perhaps as much as all of the surface oceans combined.

There are 2 theories for where the mantle’s water came from:

1) Surface oceans, carried underground by subduction/plate tectonics.

2) The water remained in the mantle from when the Earth originally formed.

Future Directions

Future isotopic analysis (deuterium to normal hydrogen) of water from the oceans, mantle and comets will sort out where the oceans water came from.

Need to determine if the whole mantle uniformly contains water, or whether there are a few isolated ‘wet spots’.

Article

Hydrous mantle transition zone indicated by ringwoodite included within diamond

Pearson et al., 2014 Nature 507:221-4

Keywords

Ocean, water, Earth, mantle, crust, comet, transition zone, rock, geology, plate, tectonics, volcano, lava, magma, ringwoodite, olivine, spectroscopy, diamond, mineral

Subject

Science, Earth and Space, Geology, ST1-8ES, ACSSU019, ST1-9ES, ACSSU032, ST1-11LW, ACSSU211, ST2-8ES, ACSSU075, ST2-9ES, ACSSU048, ST2-12MW, ACSSU046, ST3-8ES, ACSSU078, ST3-9ES, ACSSU096, ST3-12MW, ACSSU077, SC4-12ES, ACSSU153, SC4-12ES, ACSSU115, SC4-13ES, ACSSU116, ACSSU222, SC5-13ES, ACSSU180, ACSSU189

Satellites discover new mountains and ridges on the ocean floor

Earth Science, Geology

Did you know that oceans cover two thirds of the planet, but only ~10% has been mapped?

For example, Malaysian airlines flight MH370 was lost in 2014 in the Indian Ocean, west of Australia, where it is almost completely uncharted.

Therefore, a more rapid method of mapping the ocean is needed.

Here, 2 satellites were used to map the ocean floor (CryoSat-2, Jason-1).

They mapped ~5,000 sea-mountains taller than 2 km (about the size of Australia’s tallest mountain Mt. Kosciuszko).

They also discovered a long ridge (800 x 100 km) along the coast of Africa that was paired with a mirror image fault line off the coast of South America.

Mapping the ocean floor is important for understanding plate tectonics, the geological history of Earth, shipping/transport routes, management of fisheries and for understanding ocean currents that influence the climate.

 

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Background

Oceans cover two thirds of the planet, but ~90% has not been mapped.

For example, Malaysian airlines flight MH370 was lost in 2014 in the Indian Ocean, west of Australia, where it is almost completely uncharted.

Mapping the ocean floor is usually performed by large research ships using echosounders. Hundreds of ships working for the past 40 years have barely covered ~10% of the ocean floor.

Therefore, a more rapid method is required.

Sediment from the continents can flow hundreds to thousands of kilometres across the ocean floor, making it appear flat and featureless. However, below it, the rock bed can have huge peaks and troughs.

Here, satellites were used to map the ocean floor.

Materials and Methods

A team of scientists from California and the University of NSW (and other places) analysed radar data from 2 satellites (CryoSat-2 and Jason-1) to map the ocean floor. They analysed >70 months of data. They map the ocean floor from the shape of the water surface above it. Water is affected by gravity, so it is pulled into highs above sea-mountains and slumps low over depressions (e.g. trenches), thereby affecting its shape.

Results

The satellites mapped ~5,000 sea-mountains taller than 2 km (about the same size as Australia’s highest peak Mt. Kosciusko).

They also discovered a new pair of tectonic features: a long ridge (800 x 100 km) along the coast of Africa, with a mirror image fault line off the cost of South America. That is, newly discovered plate tectonic features.

Discussion

Mapping the ocean floor is important for understanding plate tectonics, the geological history of Earth, shipping/transport routes, management of fisheries (animals congregate around sea-mountains), and for understanding large ocean currents that influence global climates.

Article

New global marine gravity model from CryoSat-2 and Jason-1 reveals buried tectonic structure

Sandwell et al., 2014 Science 346:65-7

Keywords

Ocean, floor, geology, Earth, satellite, mapping, map, tectonic, plates, ridge, continent, mountain, gravity, fault, peak

Subject

Science, Earth and Space, Geology, ST1-8ES, ACSSU019, ST2-8ES, ACSSU075, ST3-9ES, ACSSU096, SC4-12ES, ACSSU153, SC4-13ES, ACSSU222, SC5-13ES, ACSSU180, ACSSU189

Bacteria discovered 2.4 km below ground

Biology, Geology

Did you know that life has been discovered 2.4 km underground?

The international Ocean Discovery Program used a research ship (Chikyu) to drill through 2.4 km of rock below 1 km of water off the coast of Japan in 2012.

This was the deepest drill ever.

Coal samples from this depth contained living microbes, even though they didn’t have any light or oxygen, and hardly any water or nutrients.

Instead, they live on methyl/carbon/organic compounds and have extremely slow metabolisms (i.e. adapted to a low nutrient environment).

It’s not yet clear if this is the only type of microbe living down there or there are lots of species.

Also, it’s not yet clear how they got down there.

If life can survive in the harsh environment down there, it can survive just about anywhere. Indeed, nearly everywhere we look on Earth we find life.

 

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Article

Microbes discovered by deepest marine drill analysed

By Rebecca Morelle, BBC News (Science and Environment) Website (Dec.16, 2014).

Keywords

Life, microbes, bacteria, drill, rock, soil, coal, crust, nutrient, metabolism, organic, ocean

Subject

Science, Earth and Space, Biology, ST1-11LW, ACSSU211, ST2-11LW, ACSSU073, ST3-11LW, ACSSU094, SC4-12ES, ACSSU153, SC4-13ES, ACSSU116, SC4-14LW, ACSSU149, SC4-15LW, ACSSU112, SC5-13ES, ACSSU189, SC5-15LW, ACSSU185

Oldest rock on Earth is not from Earth

Astronomy, Geology

Did you know that the oldest rock on Earth is actually from Mars?

It’s called Black Beauty and it’s 4.4 billion years old.

It’s owned by a doctor/amateur meteorite collector from America.

It’s worth >$10,000 per gram (gold is ~$40 per gram) and he has ~800g of it.

Around 5 million years ago, an asteroid struck the surface of Mars, blasting the rock into space.

Then sometime within the last 1000 years, it landed on Earth as a meteorite (found by a nomad in the Western Sahara).

It’s particularly interesting because it’s a sedimentary rock containing water (from 4.4 billion years ago), therefore perfect for harbouring fossilised life forms (if there ever was life on Mars).

It’s currently being analysed by museums around the world.

 

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Article

Martian Obsession, by Eric Hand. Science, 2014. 346:1044-9.

Further Reading

Origin and age of the earliest Martian crust from meteorite NWA7533

Humayun et al., 2013 Nature 503:513-6

Keywords

Mars, Earth, space, meteorite, rock, sedimentary, water, fossil, asteroid

Subject

Science, Earth and Space, ST3-8ES, ACSSU078, SC4-12ES, ACSSU153, ACSSU115, SC5-12ES, ACSSU188, SC5-13ES, ACSSU180