You can do it all -- if you take the time....

“We want to go to the lava flow and then to a waterfall,” they said.  I chuckled and replied, “You want two days then.”  As many do, this couple hadn’t comprehended some important facts-on-the-ground of the “Big Island.”

As much as attuned residents of the Island of Hawai`i prefer to call it by its Polynesian names (usually, just Hawai`i, often with a soft “v” sound for the “w;” Moku o Keawe is another), there’s no denying that the more tourism-promotional name is accurate: It is a big Island.   A bit smaller than Connecticut, the Island is slightly less than four times the surface area of Rhode Island and more than twice as big as Delaware. The entire State of Hawai`i comprises 6,423 mi.² and the other islands in it could be accommodated within the boundaries of the largest with considerable space to spare.  It can be a long journey from one part of the “Big Island” to another.

There is no road that completely encircles the Island of Hawai`i.  The north, south and east extremities are accessed only by means of side-roads.  This reflects the rugged complexity of the terrain and the fact that land development is scattered on the Island.  From the north to the south ends of the Island a straight-line measurement yields a distance of 93 miles; from east to west, 76 miles.  These figures don’t reflect the fact that any effort to travel such lines would involve scaling volcanic mountains that count as being among the earth’s most massive features – Mauna Kea, as the highest volcano in the Pacific, and Mauna Loa, as the planet’s most massive mountain, though 117’ closer to sea level than its neighbor.

And speaking of volcanoes, let’s return to the quandary facing the hikers who wanted to see flowing rock (it should be said here that eruptions are not constantly in effect; decades may pass without one) and water spilling over a fall as part of a same-day experience: it can be done, but not with the quality of time in either venue that would make for anything approaching a complete and satisfying visit.  So much time would be expended in getting from one location to the other that everything would feel rushed.  Though imaginative painters sometimes portray flowing lava as colorfully pouring down slopes adjacent to steep sea cliffs clad with lush vegetation and plunging waterfalls, anyone who has observed Hawai`i’s landscapes with a careful eye knows that the two are not juxtaposed. The reason, explicable in the languages both of science and of myth, has to do with the relative ages of the landforms in which these two expressions of nature – molten rock and plunging water – are to be found.

Hawaiian volcanoes in their younger and middle-age eras tend effusively to erupt molten rock.  Hawaiians identified two major types of lava (and scientific geology has generally followed their designations): pahoehoe, the smoother, billowy, continuous sheet flows; and ‘a’a, broken piles of clinker and rubble.  Whichever form such erupted material takes, even pounding rain doesn’t do much in the way of erosion, tending rather quickly to be percolated from the surface to the interior of the rocky ground.  When they reach senior-age status the volcanoes of the Hawaiian Islands tend to erupt more explosively, ejecting finer material into the air for deposit on the surface as cinder and ash.  When rain falls on this sort of layer, it does begin to cut down into it, forming streams -- given that the material is deep enough and the rivulets accumulate enough volume.  As streams grow in size, they also grow in power.  Eventually significant cutting into the underlying lava occurs.  Since lava flows vary in hardness (porosity being a major determinant and generally associated with gas-induced vesicles in the rock), they will erode at differential rates.  When a stream cuts down through some rock faster than it does other rock, waterfalls appear.  The more prevalent are waterfalls, the older the land.  Evidence for this is seen in the rugged landforms and plunging streams of the older of the major Hawaiian Islands, and the fact that on the Island of Hawai`i proper, waterfalls are found only on the oldest of its volcanic mountains.

The soaring cliffs characteristic of some parts of the Hawaiian Islands are also age-related.  The action of the sea is consistent in gnawing away at the shoreline, undercutting edges that collapse and leading to over-steep slopes that give way to cataclysmic landslides changing the shape of the islands and littering the ocean floor with miles of massive debris.  In general, then, the higher are the sea cliffs, the older the land.

© 2008 Hugh R. Montgomery, Ph.D.