Christchurch City (population 320,000) sits at the base of the long arc of
Pegasus Bay, bounded to the north by the Waimakariri River and to the
south by the old crater complex of the Port Hills and Banks Peninsula.
The heavily braided rivers of the South Island of New Zealand bring
greywacke rock from the Southern Alps to the west, forming the huge
alluvial pan (750,000 ha) of the Canterbury Plains. Braided rivers are
rare worldwide, found elsewhere only in Alaska, Canada, and the Himalayas.
They form a network of ever-changing channels weaving between temporary
shingle islands. In some places, the gravel they have transported from the
mountains formed by the clash of the Indo-Australian and Pacific Plates is
as much as 500 meters deep.
Banks Peninsula, named for explorer Captain Cook’s botanist, consists of
two overlapping extinct volcanoes, the Lyttelton Volcano and the Akaroa
Volcano. Since the last eruptive activity some six million years ago, the
volcanoes have been heavily eroded, dropping them from a peak of 1,500
meters down to around 500 meters.
During his quick 1770 visit, Cook mistook the peninsula for an island, but
the build up of the Canterbury Plains has seen it joined to the mainland
for at least 200,000 years.
Breaches in the crater walls have produced two long harbors: Lyttelton to
the north and Akaroa to the south. The former is the port for
Christchurch, and European settlers in the 1860s were quick to bore a
tunnel through to Christchurch rather than tackle the steep hills and long
swampy walk into the early settlement. The original idea was to settle at
the end of Lyttelton Harbour, but the huge mudflats exposed at low tide
put paid to that plan.
The shallow green waters of Lake Ellesmere (Waihora) to the south of the
city offer a refuge for wildlife. The estuary for the small Avon and
Heathcote rivers, just to the north of Lyttelton Harbour, is home to
godwits, curlews and other visitors from Siberia and Alaska, as Asian and
American birds reach the southernmost point of their annual migrations
This image was acquired by the Enhanced Thematic Mapper plus (ETM+) sensor flying aboard the Landsat 7 satellite on September 25, 2001.