History
Although Lake Ellesmere / Te Waihora is less than 5000 years old it has undergone many dramatic changes over that short period of time. The lake is a dynamic feature, it has been up to twice its present depth and area in the past, and it has progressed through various stages as it has developed into the brackish bar-type lagoon that we see today. In Chronological order these stages began with the lake as part of Canterbury plains, which were then flooded, forming a bay, then an estuary and finally a lake/ lagoon (Waituna type lagoon).
The original formation of Lake Ellesmere / Te Waihora was primarily a function of formation of Kaitorete Barrier. Kaitorete Barrier is often incorrectly referred to as a spit. However by definition this is incorrect as a spit is widest at the updrift end and tapers to a narrow tip at the downdrift end, but the Kaitorete Barrier is narrower at the southern (updrift) end and widest at the northern (downdrift) end. Kaitorete is also attached to the land at both ends (although somewhat tenuously in south) and therefore technically classed as a Barrier beach.
The formation of Kaitorete Barrier began at the end of the Last Glacial Maximum 20,000 years ago valley glaciers advanced in Canterbury and subsequent glacial outwash rivers delivered vast quantities of sand, gravel and silt to the coast. Sea level in Canterbury was 130 meters lower than the present day due to glaciation and the coast was as far as 50 km east of its present day position, meaning the Canterbury plains were double their present width. Subsequent rapid sea-level rise then drowned what is now the continental shelf, causing rapid westward migration of the coast. 10,000 years ago the Canterbury coast was approaching the area presently occupied by Lake Ellesmere / Te Waihora. The coast consisted then, as it does now of the unconsolidated sands and gravels of the fans of major rivers in the area such as the Rakaia and Waimakariri. The Canterbury Bight was exposed to powerful southerly waves. The combination of weakly resistant unconsolidated sands and gravels and high energy wave action caused rapid coastal erosion and strong net northward transport of the resulting load of sands and gravels fed to the shore.
This completes the sequence of events leading up to the formation of Lake Ellesmere / Te Waihora; with rapid sea-level rise drowning the seaward edge of plains, rapid erosion of coast to south changing its position and providing, in addition to direct river-borne sediments, a massive supply of sea borne sediments and strong net northwards longshore drift by waves, moving the sediments towards Banks Peninsula and providing the materials to construct Kaitorete Barrier, that now encloses the lake.
If left to develop naturally Lake Ellesmere / Te Waihora will once again become a saltwater estuary over the next few centuries.
Read more about this topic: Lake Ellesmere / Te Waihora
Famous quotes containing the word history:
“What would we not give for some great poem to read now, which would be in harmony with the scenery,—for if men read aright, methinks they would never read anything but poems. No history nor philosophy can supply their place.”
—Henry David Thoreau (1817–1862)
“To care for the quarrels of the past, to identify oneself passionately with a cause that became, politically speaking, a losing cause with the birth of the modern world, is to experience a kind of straining against reality, a rebellious nonconformity that, again, is rare in America, where children are instructed in the virtues of the system they live under, as though history had achieved a happy ending in American civics.”
—Mary McCarthy (1912–1989)
“The history of modern art is also the history of the progressive loss of art’s audience. Art has increasingly become the concern of the artist and the bafflement of the public.”
—Henry Geldzahler (1935–1994)