Six of the port districts are located on the Columbia above the head of deep navigation, where barge traffic is composed principally of grain and petroleum downstream and cement and structural steel upstream.
Nearby, at the head of deep and quiet valleys like Eskdale and Wasdale, the central massif of England's fabled Lake District builds like the hub of a great spoked wheel around mountains like Scafell Pike and Great Gable, Pillar and Bowfell, the tallest and toughest — though hardly Alpine — assemblage of peaks in the land.
But James Dupree, head of deep-water production in the Gulf of Mexico for BP, predicts that, in a decade's time, a similar map will show the infrastructure extending out to waters where the depth is more than 5,000 feet.
The port of New Orleans ranks among the busiest in the country in volume of seaborne freight, while Baton Rouge, farther up the Mississippi River at the head of deep-channel navigation, is important for shipping of petroleum and chemical products, including aluminum and grain.
The first time Michael Fedak told other researchers he wanted to study climate change by fixing satellite-connected sensors to the heads of deep-diving ocean mammals, the University of St Andrews biology professor was laughed at.
At Anavik, the Viking farmstead built at the head of a deep fjord east of Nuuk, I sat on a lichen-encrusted granite block, hewed by Viking hands almost a millennium ago.
After five days the party took the boat a short distance eastwards, to the head of a deep bay which would be the starting point for the crossing.
"It's an amazing new world," said Robert Hazen, head of the Deep Carbon Observatory, a decade-long $500 million project to study the planet's carbon, an element vital to life and found in everything from oil to diamonds.
Itháki (Vathý), the chief place and port of the island, is well protected at the head of a narrow, deep, horseshoe-shaped inlet of the gulf.
KP's first ball from Dockrell saw him mistime a drive just over the head of Hildreth at deep mid-off.
In 2013 at the Schmidt Ocean Institute conference, she met Peter Girguis, head of Harvard's deep sea lab, and Erik Cordes, who has made over 35 dives in the Alvin.
