Saturday, June 30, 2012

Impact Craters

The moon and the earth were bombarded by many large and small meteorites and comets during the first 500 million years of the Solar System.
Gosses Bluff impact crater
in Northern Territory, Australia

The earth has about 180 identified impact craters. In contrast, the remains of thousands of impact craters are visible on the moon.

The moon's surface is comparatively static, while earth's surface is an ever-changing system with plate tectonics, mountain formation, and erosion.

Over geological time, most of earth's impact craters are:
  • Eroded away;
  • Obliterated by mountain building;
  • Buried by younger deposits; or
  • Inundated by oceans and fresh water.
Greenland's Maniitsoq Crater

Discovery in Greenland

The remains of a 3000 million year-old meteorite impact was discovered on the western coast of Greenland in 2009 by a GEUS geologist. The crater impact structure found near the town of Maniitsoq is about 310 miles wide.

Until the discovery of the Maniitsoq impact crater, the 2020 million year-old, 186 miles wide Vredefort crater in South Africa was believed to be earth's oldest (and largest) impact structure.

The oldest identified impact craters are shown in the table below:

Name Location Diameter
(million years)
Maniitsoq Western Greenland 310 3000
Vredefort South Africa 186 2020
Yarrabubba Western Australia 19 2000
Sudbury Ontario, Canada 155 1850
Keurusselkä Western Finland 19 1800
Amelia Creek Northern Territory, AU 12 1660-600
Shoemaker Western Territory, AU 19 1630
Strangways Northern Territory, AU 16 646
Beaverhead Idaho / Montana, US 37 600
Acraman South Australia 56 590
Facts which at first seem improbable will, even on scant explanation, drop the cloak which has hidden them and stand forth in naked and simple beauty.
~ Galileo Galilei

Saturday, June 23, 2012

Fire and Life

Uncontrolled wildland fires occur naturally. Wildfire is an integral part of its ecosystem.

Fire Ecology is the study of fire dependence, the adaptation of plants and animals to wildfires, and fire effects on ecosystems.
No matter how intently one studies the hundred little dramas of the woods and meadows, one can never learn all the salient facts about any of them.
Aldo Leopold

High Park Fire

The High Park fire is burning in the Arapaho and Roosevelt National Forests and the Pawnee National Grassland in north central Colorado. Thick timber and large stands of Mountain Pine Beetle-devoured trees provide the fuel.

NASA satellite image of the High Park Fire.  June 10, 2012
High winds and hot, dry weather caused the High Park fire spread rapidly over tens of thousands of acres.

Fire and Life

Lodgepole Pine Cone
Many plant species require fire to germinate, establish, or reproduce.

The Lodgepole Pine depends on fire to germinate, establish, and reproduce. Lodgepoles produce resin-coated, serotinous pine cones.

The resins seal the scales of the cones protecting the seeds inside. Lodgepole seeds often remain sealed for decades.

Eventually a passing fire provides enough heat to melt the resin. The cone scales open up to release their seeds to the forest floor. Without wildland fires, Lodgepole seeds would likely never be released.

The heat from the fire does not penetrate the soil more than a few centimeters. This affords the seeds the required nutrients to quickly germinate and to give life to a new generation.


Saturday, June 16, 2012

Atmospheric Oxygen

Where does earth's oxygen come from?

Microbes in the world's oceans provide about half of the earth's oxygen. Macro algae, like kelp, and land plants provide the other half.

A two gallon pail of sea water contains more bacteria then the earth's human population. For perspective, recent estimates put the volume of the Earth's oceans 352 quintillion (1018) gallons of water.

On the boundless expanse of the oceans,
“Doesn't it seem to you," asked Madame Bovary, "that the mind moves more freely in the presence of that boundless expanse, that the sight of it elevates the soul and gives rise to thoughts of the infinite and the ideal?”
Gustave Flaubert, Madame Bovary
Incredibly one marine species, prochlorococcus, produces 20% of all atmospheric oxygen.


Prochlorococcus is the single-most abundant phytosynthesizer on earth. It is the ocean's oxygen producing powerhouse.

MIT marine microbiologist Melissa Garren calls prochlorococcus the
"invisible engineers that control the chemistry of the ocean"
While producing 20% of earth's oxygen, marine microbiologists didn't discover prochlorococcus until 1986.
"We have an incredibly important relationship with these marine microbes that have very large scale consequences and we're just barely beginning to understand what that relationship looks like and how it may be changing."
Melissa Garren


Saturday, June 9, 2012

Planetary Life Raft

For every year I live, I ease my criteria for what constitutes the natural world. My criteria for naturalness has softened.

At age twenty, the bar of naturalness was set by the ever-elusive absence of human trace – no human structures, sights, smells, or discarded Ding Dong wrappers.

Yes, humans are an untidy species.

Michael Pollan reminds us of our unwavering codependency on flora and fauna. Other animals and flowers have changed us. We, in turn, have changed them.
It has become much harder in the past century to tell where the garden leaves off and pure nature begins.
Michael Pollan
In The Botany of Desire Pollan explores the co-evolution of humans with four plants — apples, tulips, marijuana, and potatoes — from the perspective of both plant and human.

Co-evolution is the notion that change in one biological object is triggered by change in a related object. I wonder about the frequency of triggering events over the course of a human lifetime. Do they occur unbeknownst to us?
Shall I not have intelligence with the earth? Am I not partly leaves and vegetable mould myself.
― Henry David Thoreau
Like other fauna and flora, humans have built-in drives, if not self-obsessed desires. Each species, animal or plant, is hell-bent on thriving in a dynamic biosphere where change is rapid, slow, and sometimes cataclysmic. To thrive we take advantage of ― and co-depend on ― other species, as they do on us.

Earth's Biosphere

How do we reckon this thin raft of life on earth? The biosphere is,
The place on Earth's surface where life dwells.
― Eduard Suess, Geologist, 1875.
Cloud Tracks
The biosphere is the sum of all ecosystems. This life raft is thin compared to a planetary scale, or the distance between the earth and the moon.

Earth's biosphere consists of all living beings and their relationships. The life-giving relationships of "earthlings" include critical interaction with the elements of the lithosphere, hydrosphere and atmosphere.

By humanity's best reckoning, earth's biosphere evolved beginning through biogenesis or abiogenesis some 3.5 billion years ago. Abiogenesis describes the so-called primordial soup. That is,
the study of how biological life could arise from inorganic matter.
No less poetic, biogenesis is
the generation of life from existing life.
In Operating Manual for Spaceship Earth, Buckminster Fuller observed that
Our little Spaceship Earth is only eight thousand miles in diameter, which is almost a negligible dimension in the great vastness of space. . . Spaceship Earth was so extraordinarily well invented and designed that to our knowledge humans have been on board it for two million years not even knowing that they were on board a ship.

Indeed my criteria for naturalness has softened over the years. Seeking an absence of human trace is an elusive and frustrating folly.

Is it not better to embrace the splendor and untidiness of life, to drop the thread of time, and to live each sensual input of the moment?
For it is only by forgetting that we ever really drop the thread of time and approach the experience of living in the present moment, so elusive in ordinary hours.
Michael Pollan
Within the Blue Spiral
When I am mindful that humans co-evolved with enumerable, and perhaps uncountable species, and when I am mindful that these species have adapted to our desires for their self-serving viability, I see the earth's biosphere as a life raft.
Earth calls in the wind, sings in the rain, and laughs in the flowers.
All life, and all artifacts of life support, are in the same boat.

Reading & References

Saturday, June 2, 2012

Chesil Beach Pebbles

Chesil Beach, Dorset
Forget not that the earth delights to feel your bare feet and the winds long to play with your hair.
~Khalil Gibran
Chesil Beach is a 18 mile coastal stretch on the south coast of England that I visited one blustery fall afternoon in the early 1990s with my wife and children ages one and four.

Chesil Beach is made up almost entirely of pebbles - an estimated 180 billion of them. It is a wondrous and curious place for children and adults alike.

Beach Physics

The pebbles diminish from potato-size to pea-size as you walk northwestward along the beach. Pebbles are transported east along the beach driven by waves. The wave action has graded the pebbles in size all the way along it.

Potato-Sized to Pea-Sized Pebbles
Of Chesil Bank, as it is known to locals, English novelist John Fowles said,
"It is above all an elemental place, made of sea, shingle and sky, its dominant sound always that of waves on moving stone: from the great surf and pounding “grounds of seas” of sou’westers, to the delicate laps and back-gurgling of the rare dead calm."
~John Fowles, English novelist (1926 - 2005)

According to local folklore, smugglers knew where they had landed from the size of the pebbles on the beach. 

Additional Reading