Volcanoes in the Hawaiian Islands form in response to hot-spot magmatism deep below the lithosphere. As a volcano is moved away from the hot spot by motion of the Pacific tectonic plate, it ceases volcanic activity and a new vent forms.
Thus, a chain of volcanoes forms along the direction of plate motion, with younger volcanoes near the position of the hot spot.
As volcanoes emerge above the sea surface, they form a gently sloping volcanic shield; the period from when a new volcano breaks the sea surface to the end of shield building is estimated to last about 0.5 million years.
Throughout the growth of a volcano and for some time after completion of its shield, weight on the thin oceanic crust causes the volcano to subside. During shield building, rapid growth outpaces subsidence and there is a net increase in height and area. However, when shield building ceases, net subsidence submerges many areas formerly above sea level.
In addition, over long time periods, erosion is an important factor in changing the topography of an island. Erosion is difficult to model because there is no accurate way to determine the timing and magnitude of all events. (Price and Elliott-Fisk)
Maui is a doublet – that is, it originally consisted of two distinct islands which were later united. (USGS) West Maui and Haleakala lava flows joined to form a broad, low isthmus. (Holthus) The 7-mile wide valleylike isthmus earned Maui the nickname of the “valley isle.” (Britannica)
“The north side of the isthmus, the location of Pauleukalo Marsh and Kanaha Pond, consists of stream-transported sediments and beach material. The marshes have formed in coastal depressions. Kanaha Pond formed in weathered lava. During floods, freshwater overflows the wetland and the barrier ridge and discharges directly to the ocean.”
“The beaches along the north side of Maui’s isthmus are discontinuous and fronted by beachrock outcrops. Beach rock up to 790 ft offshore from the present beach indicates a general trend of erosion over the last few hundred years.”
“The south side of Maui’s isthmus supports a 4 mi long, gently curved barrier beach which separates Kealia Pond from the ocean. Water level fluctuates seasonally, forming a 400-500 acre shallow, brackish pond in winter and spring, and exposing extensive red-brown mudflats in summer.”
“The wetland is slowly filling with stream-transported deposits of terrigenous material and wind-blown beach sands. The pond’s
drainage outlet is periodically blocked by sand, but clears during heavy streamflows.” (Holthus)
The abundance of water in Nā Wai ʻEhā ((“The Four Great Waters”) – Waiheʻe River, Waiehu Stream, Wailuku (ʻĪao) Stream and Waikapū Stream are in central Maui) enabled extensive loʻi kalo (wetland kalo) complexes, including varieties favored for poi-making such as “throat-moistening lehua poi.” (CWRM)
Nā Wai ʻEhā once “comprised the largest continuous area of wetland taro cultivation in the islands.” Its “complex agricultural system of wetland kalo cultivation,” together with the abundant protein sources in the streams and nearshore waters, supported one of the largest populations on Maui.
The fertile kalo lands, complex system of irrigation ʻauwai (ditches) and abundant fresh water from Nā Wai ʻEhā sustained Hawaiian culture for 1,000-years.
Given the makeup of the Nā Wai ʻEhā, Waiheʻe River and ‘Īao historically would have flowed continuously to the coast; Waiehu Stream would have flowed continuously to the coast at least 95 percent of the time; and Waikapū Stream would have flowed continuously to the coast less than half of the time. (USGS)
While water was flowing in the river valleys, in about 1840 it was estimated that, “The isthmus is too dry to be fit for cultivation; it is in extent about twenty by fifteen miles. During nine months of the year it is a fine grazing country, and feeds large herd of cattle, that are mostly owned by foreigner.” (Wilkes (1840-41))
“The district of Wailuku is composed of valley and upland. The soil in the former is extremely rich and well watered; the upland, also, produces good crops when sufficient moisture can be had. Potatoes, corn, sugar-cane, and sweet potatoes, are the chief products of the windward side of the island.” (Wilkes)
“Between the beaches of Kahului and those of Maalaea and Kalepolepo lies a vast expanse of level land, forming an isthmus connecting east and west Maui, which as it exists is fit for nothing except the pasturage of animals and in some places not even fit for that owing to an entire destitution of water supply.” (Pacific Commercial Advertiser, June24, 1876)
“The area of this land is perhaps not less than fifty thousand acres, and capable, if irrigated, of producing many thousand tons of sugar. Most of this belongs to the government, and if the spirit of enterprise were rife among those in authority …”
“… this whole plain could be turned into a garden, for there is an abundance of water running waste upon the highlands of Haleakala amply sufficient if utilized for this purpose to supply the entire tract.”
“The subject of irrigation of this plain has been more than once brought forward for consideration, but no thorough investigations have been divulged, if they have ever been made, as to the best means of bringing down the waste water on to it, or the probable expense that would accrue, although the feasibility of the project is not to be doubted.”
“During the reign of Kamehameha V, some investigations were said to have been made, but as to their nature or comprehensiveness the public were allowed to remain in the dark, or to be satisfied with the dicta of his imperious ministry, that the engineering would be too costly and the whole affair too ponderous to be handled by the government.”
“This is certainly one of our first and greatest needs, and with reciprocity to back us there would be no fear of the result… We have heard of a suggestion to irrigate this plain, or a part of it, by water derived from the streams of Waiehu and Waihee, much of whose water now runs to waste.” (Pacific Commercial Advertiser, June24, 1876)
By the 1870s, growing plantation interests in the region sought out ways to turn what had become almost desolate isthmus lands and neighboring kula lands of Maui, green with cane.
Their economic plan was made viable by the passage of a Reciprocity Treaty between the United States and the Hawaiian Kingdom on January 30, 1875; and subsequent ratification of the treaty by King Kalākaua on April 17, 1875.
The treaty went into effect on September 9th, 1876, and on September 13th, 1876, King Kalākaua granted issuance of the first Water License for construction of the “Haiku Ditch,” and drawing water out of streams of the Hāmākua Loa District.
The initial development of the ditch system was authorized as a part of the Hawaiian Kingdom’s program to promote prosperity for all the people of the Kingdom. (Kumupono)
Sugar was planted and the West Maui streams were diverted. In addition, five ditches originating in East Maui at different levels are used to convey the water from that region to the cane fields on the isthmus of Maui.
In order of elevation they are Haiku, Lowrie, Old Hamakua, New Hamakua, and Kailuanui ditches. They cross about 20 gulches east of Maliko, all of which have more or less water at all times and large quantities after storms. (USGS, 1910-1911)
Wailuku Sugar was organized in 1862 by James Robinson, Thomas Cummins, J Fuller and agent C Brewer. In 1878, through his friendship with King Kalākaua, Claus Spreckels secured a lease of 40,000-acres of land on Maui and by 1882 he founded the Hawaiian Commercial Company (later known as Hawaiian Commercial & Sugar Company – HC&S.)
The late-1890s saw internal family conflicts. Spreckels lost control of HC&S and in 1898; it became a part of Alexander & Baldwin Co. Following the 1948 merger of HC&S and Maui Agriculture Co., HC&S became a division of Alexander & Baldwin.
Fast forward to December 2016, Hawai‘i saw its last sugar harvest on the Maui isthmus. In December 2018, Alexander & Baldwin (A&B) announced that it had sold its 41,000-acre sugar plantation in Maui’s central plains to Mahi Pono LLC, a joint venture between Pomona Farming LLC, a California-based agricultural group, and the Public Sector Pension Investment Board (PSP Investments), one of Canada’s largest pension investment managers.
Much of the sugar land is now in diversified farming (with orchard and row crops such as lime, lemon, orange, tangerine, coffee, avocado, macadamia nut, ‘ulu, onion, kale, lettuce, watermelon, bananas, coconut, and lilikoi) by Mahi Pono.
As of December 2022, Mahi Pono had planted more than 1.64 million trees on approximately 8,625 acres of land. In addition to our tree plantings, we have also prepared over 9,000 acres of grass pastureland to support our Maui Cattle Company grass-fed beef operations. Their products are typically sold under the Maui Harvest brand. (Mahi Pono)
