Driftwood

Adrian Pingstone

Wood and water make agreeable travel companions.

If not trapped in an eddy, driftwood will cover great distances traveling with the current of moving water.

A flat rock skipped across water eventually sinks. Wood floats.

Why does wood float and driftwood drift?

Archimedes wrote on parchment in his treatise On Floating Bodies,

Any floating object displaces its own weight of fluid.
— Archimedes of Syracuse

On Floating Bodies

On Floating Bodies is the first recorded work on hydrostatics. Archimedes found the buoyancy of a solid was determined by its form and its specific gravity.

Specific gravity is the ratio of the density of a substance to the density of a reference substance.
— Wikipedia

Most wood floats on water because most wood is less dense than water.

The ratio of the density of white ash to the density of water is less than one, or about 0.7, so white ash floats.

Balsa is a particularly buoyant wood with a specific gravity of 0.16. Balsa has a density of 160 kg/m³. For comparison, the density of water is 1000 kg/m³. Balsa wood rides high on the water.

Thought Experiments

Wood	Place a full glass of water in a pie tin. Place a small block of wood in the water. It floats! A small amount of water spills into the pie tin. If you weighed the spilled water, it would equal the weight of the wood. The wood displaces its own weight. Wood is less dense than water.

Denser woods like box wood or ebony will sink because they are denser than water.

Rocks and minerals are denser than water so they will sink. Rocks are too dense to displace their own weight in water.

Rock	Place a full glass of water in a pie tin. Place a small rock in the water. It sinks! A small amount of water spills into the pie tin. If you weighed the spilled water, it would be less than the weight of the rock. The rock is unable to displace its own weight. Rocks are more dense than water.

Driftwood that had traveled from places unknown to the place I was standing was having a temporary layover (video below) on the Mississippi River. The driftwood was trapped between a submerged rock and the sandy shoreline as it was buffeted by wave cycles.



REFERENCES

• On Floating Bodies, Archimedes of Syracuse (287 BC – c. 212 BC)
• Specific Gravity, Wikipedia.
• Wood Density, The Engineering Toolbox.

The Anthropocene

Anthropocene word origin

Anthropocene is a 21st century term popularized by atmospheric chemist and nobel laureate Paul Crutzen for what will perhaps be recognized as a new geologic epoch.

The roots of the word are anthropo- for man and cene for new.

No date is recognized as the start of the Anthropocene, but atmospheric data seems to point to the early 19th century industrialization that occurred during the time of the Industrial Revolution. Other scientists indicate it should start with the Atomic Age of the 1950s.

The Anthropocene was preceded by, or is encompassed by, the Holocene which, in turn, was preceded by the Pleistocene

The Holocene began about 11,700 years ago and includes the growth of the human species. The Pleistocene lasted from about 2,588,000 to the Holocene and spanned the most recent period of repeated glaciations.

Shanghai at sunset

The Anthropocene is marked by the characteristics of:

• over-population (fourfold increase in the 20th century alone);
• the greenhouse effect;
• warming temperatures;
• melting glaciers;
• rising sea levels;
• frequent weather extremes; and
• overall climate disruption.

All of these characteristics are widely held to be linked to human activities.

"Two billion years ago, cyanobacteria oxygenated the atmosphere and powerfully disrupted life on earth. But they didn’t know it. We’re the first species that’s become a planet-scale influence and is aware of that reality. That’s what distinguishes us."
— Andrew Revkin

REFERENCES

• Anthropocene, Wikipedia.
• Coping with the anthropocene: How we became nature, De Gruyter, ScienceDaily, 17 March 2015.
• What is the Anthropocene and Are We in It?, Smithsonian Magazine, January 2013.

A Function of the Universe

image: Hubble Heritage Team

Einstein noted the deceptive chicanery of human consciousness that makes us experience a separateness from the flow of the universe.

"A human being is a part of the whole called by us universe, a part limited in time and space. He experiences himself, his thoughts and feeling as something separated from the rest, a kind of optical delusion of his consciousness. "
— Albert Einstein

Einstein felt we must disabuse ourselves of this notion.

"Our task must be to free ourselves from this prison by widening our circle of compassion to embrace all living creatures and the whole of nature in its beauty."
— Albert Einstein

All indications are that humans are dynamic systems within a dynamic system. We are dynamic systems composed of an infinitesimally smaller series of dynamic systems within an infinitely larger series of dynamic systems.

image: Σ64

We find ourselves an integral part of the sum of all ecosystems existing for a limited time on a planetary life raft that surrounds our home planet.

Buckminster Fuller noted that we reside as passengers on a planetary spaceship. Our spaceship is composed of finite life-supporting resources. Our rotating spaceship is speeding around a traveling sun.

Earth is an automated Spaceship speeding rotatively at 66,000 miles per hour around the sun, which in turn, is on its own course at 6.0 kilometers per second within the Galactic Nebula.
― Buckminster Fuller

Fuller considered humans neither fixed, nor stationary. Rather he considered humans a process, rather than a thing.

I live on Earth at present, and I don't know what I am. I know that I am not a category. I am not a thing — a noun. I seem to be a verb, an evolutionary process — an integral function of the universe.
― Buckminster Fuller

REFERENCES

• Buckminster Fuller, Wikiquote.
• I Seem to be a Verb, Buckminster Fuller, Bantam, 1970.
• Operating Manual for Spaceship Earth, Buckminster Fuller.
• Planetary Life Raft, GrokEarth, 9 June 2012.

Superior Ice Caves

The story of earthly natural wonders often begins over a billion years ago. Such is the case with mainland ice caves on the south shore of Lake Superior.

Tracing origins is like descending a rabbit hole of history because choosing a start date is elusively arbitrary. This story begins, albeit arbitrarily, with some widely accepted hypotheses of the conditions leading up to what we now can experience in the Lake Superior ice caves.

Over one billion years ago, sandy minerals were carried several hundred miles northward by rivers and braided streams.

One Billion

Over one billion years ago, rivers flowing north transported suspended particles of eroded minerals that fell out of suspension as the water's velocity slowed to be deposited the into a low-lying basin where the ice caves are today.

Sandstone section

Millions

Millions of years ago, the minerals transported by rivers into the basin eventually cemented into the friable sedimentary rock called sandstone. The sandstone of this area is known as the Bayfield group. Bayfield group sandstone has about 75% quartz, with lesser amounts of feldspar, mica, iron oxide, chert, and ferromangesian minerals.

Thousands

Thousands of years ago, receding glaciers carved cliffs from the sandstone along parts of the south shore of what is now Lake Superior.

Hundreds

Centuries of erosive wave action from the lake, and centuries of seasonal freezing and thawing has carved arches, chambers, and passageways into the sandstone cliffs. Sandstone is porous so it has the capacity to store and percolate water.

Lake Superior ice cave

image: Jeff the quiet

Today

Today, when lake ice conditions are stable and greater than 10 inches in thickness, curious people can hike along the frozen shoreline to peer into the ice caves.

The cave you fear to enter holds the treasure you seek.
― Joseph Campbell

REFERENCES

• Apostle Islands Sea Caves, Apostle Islands National Seashore, National Park Service.
• Mainland Sea Caves - Ice Caves, Apostle Islands National Seashore, National Park Service.