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.

Breaking Waves

Repeated variations on a theme play out continually in nature. Variations like the micro-scale formation of snow crystals we imagine, the large-scale diurnal and seasonal cycles we experience, or the many variations of fresh and saltwater waves we see.

Breaking wave
North Piha, west of Auckland

Fresh and saltwater waves abound:

• Breaking waves like those created by a coastal shore break;
• Stationary waves like those created by sudden jumps in the contour of a riverbed; or
• Traveling waves like those created by a pebble tossed into a still pond.

The underlying theme of a breaking wave is that the wave steepens until its crest becomes unstable, then breaks.

"The world is full of magical things patiently waiting for our wits to get sharper."
― Bertrand Russell

A shore break is grand, unrelenting, ever-changing, yet somehow the same. Breaking waves are the narrative of the ebb of flow of energy and the story of entropy.

Breaking wave on Lake Superior. Photograph by Tim Case

Each wave builds, crests, and dissipates its energy into a rush of white water.

Breaking waves fit into the cosmological theme of well-ordered to less well-ordered that plays out continually in nature.

Observing breaking waves is calming and meditative, if not hypnotic.

“Breathing in, I calm body and mind. Breathing out, I smile. Dwelling in the present moment I know this is the only moment.”
― Thich Nhat Hanh, Being Peace

Waves embody the repetition of a pattern. They demonstrate the infinite and subtle variations on how a single pattern can unfold.

The beginning, the middle, and the resolution of a wave is the same on a grand scale, but infinitely different in detail.

“Thanks to impermanence, everything is possible.”
― Thich Nhat Hanh

REFERENCES

• Being Peace, Thich Nhat Hanh
• Breaking Wave, Wikipedia.

Water Revolutions

Temperature starts revolutions.

Probe any natural phenomena with the 5 Whys. Prepare yourself to leap from the concrete and observable to the speculative and spiritual by the third why.

I keep six honest serving-men
(They taught me all I knew);
Their names are What and Why and When
And How and Where and Who.
— Rudyard Kipling, excerpt from the tale of The Elephant's Child

If you examine any natural phenomena with the 5 Whys, one why is usually down to temperature. Temperature seems to be the engine of flow in much of nature.

Temperature drives change. It starts revolutions.

Fresh Water Lakes

"Who comes to a lake for water and sees the reflection of moon?"
― Rumi

Lake water undergoes a temperature-driven revolution during each seasonal cycle.

During the hottest and the coldest time of the year, lake water temperatures are sharply stratified from top to bottom. On the contrary, during the transitional periods from cold to warm, or from warm to cold, the water temperature in lakes overturns to become well-mixed (i.e., nearly homogeneous from top to bottom).

Seasonal Temperature Profile of a Lake in the Northern Hemisphere

Great Northern Loon

Temperature stratification is experienced by swimmers. During warm months, swimming near the surface, the water is pleasantly warm. Diving down to swim at depth, the water is refreshingly cool.

"When you swim you don't grab hold of the water, because if you do you will sink and drown. Instead you relax, and float."
― Alan Watts

The depth where the water temperature changes most rapidly, is the thermocline depth, or metalimnion.

During the coldest months, lakes might ice over. Ice and snow cover reflect incident solar radiation. A cold strata of denser water will overlie the less dense, warmer water below. Stratification foments ripeness for change.

Sunset over the ice of Lake Superior

Cause and effect of the seasonal overturn of lake water is orchestrated by the inter-related properties of water:

1. Temperature changes density; and
2. Density changes buoyancy.

The stratification that occurs during temperature extremes is inherently unstable, just as the well-mixed water of the transitional seasons is ripe for stratification.

The revolution is ongoing, repetitious, and sublimely beautiful in its simplicity.


REFERENCES

• Just So Stories, 1902, by Rudyard Kipling.
• Thermocline, Wikipedia.
• Lake Ecosystem, Wikipedia.