Sensory Navigation

Reoccurring patterns of long-distance travel by migratory animals is a compelling mystery of sensory and behavioral biology.

Hatchlings

US Fish & Wildlife Service

Salmon, sharks, elephant seals, and sea turtles traverse oceans swimming thousands of miles before returning to their natal home to breed.

Sea turtle hatchlings emerge from nests in soft coastal sand to begin their fateful trek to the ocean.

Avoiding predators, the waddling hatchlings wade into the ocean.

Beyond the roiling shore break, our intrepid new swimmers set a course toward the open sea. They establish and maintain their bearings long after the sight of land recedes in the distance.

How do turtles navigate with such exactitude?

Loggerhead

Damien du Toit

Sea turtles like the loggerhead propel themselves over great expanses of ocean. Young loggerheads navigate more than 9,000 miles in the North Atlantic before returning to their origin.

Year after year, loggerheads follow reoccurring travel patterns seemingly without the aid of navigational reckoning over vast stretches of featureless water.

Following years in the open sea, juveniles find their way to familiar feeding grounds:

... juvenile turtles take up residence in coastal feeding grounds and show great fidelity to their feeding sites, homing back to specific locations after long migrations and experimental displacements. Similar navigational abilities exist in adult turtles, which migrate considerable distances between specific feeding areas and nesting beaches.
— Lohmann Lab, University of North Carolina, Chapel Hill

Marine biologists postulate that sea turtles use Earth's magnetic field as a navigational aid. Two magnetic elements, inclination angle and intensity, vary across the globe creating geomagnetic signatures for geographic areas.

Lohmann, et al hypothesize that loggerhead hatchlings remember the signature of the magnetic field of their breeding ground then use this geomagnetic imprinting as a homing cue.

Brothers and Lohmann analyzed 19 years of loggerhead nesting data on Florida's east coast.

"We reasoned that if turtles use the magnetic field to find their natal beaches, then naturally occurring changes in the Earth's field might influence where turtles nest."
— J. Roger Brothers

Brothers and Lohmann found correlation between the locations of loggerhead nests over time and known shifts in the geomagnetic field.

"People have been on earth in our present form for only about 100,000 years, and in so many ways we’re still ironing out our kinks. These turtles we’ve been traveling with, they outrank us in longevity, having earned three more zeros than we. They’ve got one hundred million years of success on their resume, and they’ve learned something about how to survive in the world.
...What turtles could learn from us, I can’t quite imagine.”
― Carl Safina, Voyage of the Turtle

REFERENCES

• Evidence for Geomagnetic Imprinting and Magnetic Navigation in the Natal Homing of Sea Turtles, J. Roger Brothers, Kenneth J. Lohmann, Current Biology, 2015.
• Geomagnetic imprinting: A unifying hypothesis of long-distance natal homing in salmon and sea turtles, Kenneth J. Lohmann, Nathan F. Putman, and Catherine M. F. Lohmann, Department of Biology, University of North Carolina, Chapel Hill, NC, July 1, 2008.
• Orientation and Navigation of Sea Turtles, Lohmann Lab, The University of North Carolina at Chapel Hill.
• Sea Turtle Migration, Wikipedia.
• Voyage of the Turtle: In Pursuit of the Earth's Last Dinosaur, Carl Safina, 2007.

Volcano of Fire

Volcán de Colima is a stratovolcano known as the Volcano of Fire. The Colima volcano has erupted several times this month.

Web cam animation of Volcán de Colima eruption

21 January 2015, 9:13AM

Volcán de Colima is in the Trans-Mexican Volcanic Belt which is a series of volcanic mountains that rise from the high plateaus of central-southern Mexico.

Our earth is very old, an old warrior that has lived through many battles. Nevertheless, the face of it is still changing, and science sees no certain limit of time for its stately evolution. Our solid earth, apparently so stable, inert, and finished, is changing, mobile, and still evolving.
— Reginald Aldworth Daly, Our Mobile Earth (1926), 320.

Crater atop Volcán de Colima

Source: Google Maps

Stratovolcanoes like Volcán de Colima are steep conical mountains characterized by periodic explosive eruptions. Stratovolcanoes have conduits that link them to magma reservoirs deep in the Earth's crust.

Strata is from the Latin stratum meaning laid down. Strato-volcanoes are built from alternating layers of hardened lava, tephra, pumice, and ash.

I am here tracing the History of the Earth itself, from its own Monuments.
— Jean André Deluc, Geological Letters Addressed to Professor Blumenbach, 1794


REFERENCES

• Our Mobile Earth, Reginald Aldworth Daly, C. Scribner's Sons, 1926.
• Principal Types of Volcanoes, USGS.
• Trans-Mexican Volcanic Belt, Wikipedia.
• Volcán de Colima, Wikipedia
• WebCam at Volcán de Colima, Web Cams of Mexico.

Island Creation in Tonga

Tonga

Tonga is an island nation of some 176 islands distributed over 270,000 square miles in the southern Pacific Ocean.

A volcano that started spewing rocks and ash last December is creating a new island.

Tonga's official island tally might soon be incremented by one.

HungaHa'apai

Geologists from the Tongan Ministry of Lands traveled by boat to study the volcano. They confirmed that a huge amount of volcanic material continues to transform the landscape.

Tongan geologists indicated the volcano is erupting from two vents. One vent is located on the uninhabited Hunga Ha'apai (red marker, right). The other is about 100 yards offshore from Hunga Ha'apai.

"The new island is more than one kilometer wide, two kilometers long and about 100 meters high"
— Ministry of Lands

Prior to the month-long eruption, the surface area of the Tongan islands was about 290 square miles. The surface area continues to expand.

"During our observations the volcano was erupting about every five minutes to a height of about 400 meters, accompanied by some large rocks... as the ash is very wet, most is being deposited close to the vent, building up the new island."
— Ministry of Lands

Rock and ash exploding from the Hunga Ha'apai volcano.

photo: AFP/MFAT

The Tongan islands lie on a global hotspot called the Ring of Fire. 75% of the world's active and dormant volcanoes lie on the Ring of Fire where continental plates collide causing seismic rumbles and volcanic eruptions. It's here that the Pacific Plate slides under the Indo-Australian Plate.

"The real difficulty about vulcanism is not to see how it can start, but how it can stop."
— Sir Harold Jeffreys, 1891–1989

REFERENCES

• Earthquakes and Mountains, 2nd edition (1950), 187, Sir Harold Jeffreys.
• Ministry of Lands, Nuku'alofa, Tongatapu, Tonga.
• Tonga, Wikipedia.
• Tongan volcano creates new island, Yahoo News, 16 January 2015.

Lake Effect Snow

Image: Aarchiba

Lake effect snow is a story of freezing winds and open water.

One snowflake consists of roughly 10¹⁹ water molecules.

Imagine icebox winds blasting across open water on an expansive lake. The whipping winds pick up moisture in the form of water vapor.

The water vapor is warmer, so it rises.

As the vapor rises, it crystallizes. Eventually snowflakes fall on the leeward shore.

The Snow Man
Wallace Stevens, 1879 - 1955

One must have a mind of winter
To regard the frost and the boughs
Of the pine-trees crusted with snow;

And have been cold a long time
To behold the junipers shagged with ice,
The spruces rough in the distant glitter

Of the January sun; and not to think
Of any misery in the sound of the wind,
In the sound of a few leaves,

Which is the sound of the land
Full of the same wind
That is blowing in the same bare place

For the listener, who listens in the snow,
And, nothing himself, beholds
Nothing that is not there and the nothing that is.

Great Lakes Surfer
Photograph by Mike Killion

REFERENCES

• Lake Effect Snow, Wikipedia.
• Warm Water and Cold Air: The Science Behind Lake-Effect Snow, NOAA

Crystalline Curiosity

Crystallization is one of the more compelling transformations in nature. That a highly ordered solid can form from solution, while a well-understood chemical process, is remarkable.

Crystal formation is observable under laboratory conditions, but for most of us, crystallization must be imagined.

Crystallization

1. The act or process by which a substance in solidifying assumes the form and structure of a crystal, or becomes crystallized.

What sparks our imagination is the observable evidence of some crystallized object whether formed over a geologic time scale like a piece of quartz we can hold in our hand, or formed from atmospheric cooling like a snow flake.

Quartz

Snow Flake

All solids have either a highly ordered arrangement of particles or a randomly distributed arrangement of particles. Our recognition of comparative orderliness might be determined by scale.

For a stone, when it is examined, will be found a mountain in miniature.
— John Ruskin, 1818-1900

Solids with a highly ordered arrangement of particles are crystalline solids, while those with randomly distributed particles are amorphous solids.

Crystalline solids have distinctively geometric shapes. By comparison, amorphous solids like coal or glass, have no discernible geometric patterns.

Diamonds, graphite, table salt and sugar are examples of crystalline solids. Crystalline solids are bounded by planes called faces. Crystal planes intersect at predictable angles.

An equal number of atoms, combined in the same way produce the same crystal forms, and the same crystal form does not depend on the nature of the atoms, but only on their number and mode of combination.
— Ellhard Mitscherlich, 1794-1863

REFERENCES

• Amorphous Solid, Wikipedia.
• Crystallization in Nature, Wikipedia
• Crystalline Solid, Wikipedia.