Life underground

Life underground

Research into the deep biosphere has just found microbes living and reproducing as deep as 5km. Some scientists have suggested that the first replicating life-forms on the planet may have originated deep underground rather than the sea/soup as commonly thought. These life forms feed not on sunlight but hydrogen and methane produced in some rocks under high temperatures and pressures.The microbes use hydrogen for fuel and methane as a source of carbon. These life forms were predicted by Thomas Gold in The Deep Hot Biosphere: The Myth of Fossil Fuels, (1999) where he also argues, controversially, that that fossil fuels  are not fossil fuels, but hydrocarbons trapped in the earth’s mantle during the formation of the earth itself  accounting for their complex organic molecules.

Closer to the surface we are in the midst of the Double-Drummer resurrection that began a few days ago at the end of the first week of December. After seven years (cicadas may count the years based on tree leafing or sap cycles) of sucking on roots of large eucalypt trees the nymphs are emerging.

Cicada hatching2
Cicada hatching

They dig their way up to the surface, climb a tree, split their exoskeleton down their back and the pale adult emerges.

Cicada hatching from its nymph stage
Cicada hatching from its nymph stage

They pump blood into their legs and then stay on the tree trunk inflating their wings with fluid as their skin hardens.

Cicada hatching1
Cicada pumping up its wings

They emerge en masse perhaps to overwhelm predation, and then last 3 to 4 weeks. They are noisy but good for the environment. Their tunnels aerate the soil and they are food for many animals, and their corpses feed nitrogen to the soil.

There are more than 200 species in Australia. Only the males ‘sing’ and they do so to call for a female. Contracting internal muscles causes musical drums in their abdomen called tymbals to buckle and produce a pulse of sound which is amplified by a hollow abdomen. These cicadas sing at 120dB. The human ear can only sustain sounds up to 120-130 dB – any louder causes pain and damage to our hearing.

At 120 dB (jackhammer level) less than 30 seconds is the accepted standards for recommended permissible exposure time for continuous time weighted average noise, according to government standards. In patches of Jagun I put my hands over my ears, the sound comes in waves, a series of crescendos. I feel sorry for the birds, I can barely hear a pair of kookaburras, probably the loudest birds in this forest.

Cicada shell
Cicada shell


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