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Geological exploration

by  Simon Nathan

The early naturalists and geologists who explored New Zealand were energetic and dedicated. They sketched, made notes, plotted maps and published reports on volcanoes, river terraces, oil seeps and mineral ores. In this natural laboratory, the rigorous standards established in the 19th century are now applied to the study of the ocean floor and other geological frontiers.


Early European exploration

The travelling naturalists

Although there was considerable knowledge of minerals and fossils at the end of the 18th century, geology had not emerged in Britain as a separate discipline of natural science. The first scattered observations in New Zealand were made by naturalists, surveyors and other travellers.

Captain James Cook and his scientific staff on the Endeavour expedition to New Zealand (1768–71) were instructed to report on all aspects of natural science, including rocks, minerals and fossils, but his naturalists Joseph Banks and Daniel Solander were mainly interested in botany and ethnography. Their journals and reports make only passing reference to geological features such as floating pumice, iron sand, stones and mineral ores.

Most European visitors came to the Bay of Islands until the 1840s, and there are several accounts of local geological features such as river terraces and volcanic cones. The missionary brothers Henry and William Williams were interested in natural science, and guided visiting naturalists around volcanic cones, hot springs and river terraces.

Although many Europeans explored and surveyed remote parts of New Zealand, little information was recorded about the geology.

Ernst Dieffenbach, explorer and naturalist

Ernst Dieffenbach, a German, spent two years (1839–41) exploring the North Island on behalf of the New Zealand Company, which was promoting the country for British settlement. He also visited the Marlborough Sounds and the Chatham Islands.

Although his prime task was to look for agricultural land and minerals, he made extensive collections of plants, animals and fossils, and a number of new species bear his name. He noted the difficulty of geological research posed by the dense forest. However, he made some of the first observations of the rocks and thermal activity in the central part of the North Island, and was the first to use the term ‘greywacke’ for the widespread grey rocks of the main ranges. His book Travels in New Zealand (1843) gave an account of the fauna, flora, landscape and Māori inhabitants of New Zealand.

Dieffenbach was keen to do a broader scientific study of the new colony once his contract with the New Zealand Company ran out. Despite support from Governor William Hobson, he was unable to obtain financial support. After he left, only scattered geological information was gathered for almost 20 years.

Overseas interest in New Zealand geology

Paleontologists in Europe were fascinated by the distinctive fossil fauna of New Zealand, especially large extinct birds such as the moa. The naturalist Walter Mantell, who emigrated from England in 1840, made large collections from different parts of the country which were subsequently described by Richard Owen, director of the Natural History Museum in London. When Mantell visited London in 1856, he and Owen reconstructed the largest moa skeleton then known, Dinornis elephantopus. Subsequently there was a strong demand from museums and collectors for moa bones.

The 1855 Wairarapa earthquake caused considerable interest in Britain. Using information from the New Zealand surveyor Edward Roberts, the eminent British geologist Charles Lyell incorporated a description of the earthquake in the 10th edition of his classic Principles of geology. This was the first time that the relationship between faulting and earthquakes was recognised.


The search for gold and minerals

The discovery of gold in Coromandel in 1852 and later gold rushes led provincial governments to seek more information on mineral resources. By this time geology had become a separate discipline in European universities, and professional geologists were being employed. They saw the earth as an object whose history could be revealed by studying rocks, fossils and strata.

Hochstetter’s exploration

When the young Austrian geologist Ferdinand Hochstetter arrived in Auckland in 1858 with the Novara expedition, New Zealand Governor Thomas Gore Browne asked him to report on the newly discovered coal deposits at Drury, in south Auckland. He was joined by Julius Haast, a German emigrant who had studied geology.

The Auckland Provincial Council was so impressed with the Drury coal report that it asked Hochstetter to continue his explorations. Over the next nine months he and Haast undertook the first systematic geological exploration of the North Island, and then visited the Nelson region.

Hochstetter left for Vienna in October 1859. In 1863 he published the Topographic-geologic atlas of New Zealand, followed by Geology of New Zealand (1864). This was the first comprehensive report on New Zealand geology, based on his own observations and information from Haast, Charles Heaphy and others. In later years Hochstetter published 21 further reports, and arranged for specialists to study his collection of fossils and other material.

Crawford in Wellington province

J. C. Crawford, a Wellington settler with wide-ranging scientific interests, undertook extensive exploration in the lower half of the North Island from 1861 to 1864, seeking mineral prospects and transport routes. Appointed Provincial Geologist in 1861, he prepared maps and reports on Wellington’s geological features.

Expensive work

Not everyone was enthusiastic about geology. Henry Bunny, a member of the Wellington Provincial Council, considered a geologist to be ‘a very expensive luxury … It is all very well for a man to be paid for going about the country picking up stones and then writing a report about them, but I at any rate do not believe in paying for it.’ 1

Haast in Nelson and Canterbury

After Hochstetter’s departure in 1859, Julius Haast made an epic exploring trip for the Nelson Provincial Council down the Buller River, following a route pioneered by the surveyor and explorer Thomas Brunner. He confirmed the large coal resource north of the Grey River, and discovered bituminous coal near Denniston (later developed as the Buller coalfield).

Haast became Canterbury’s provincial geologist in 1861, and made several expeditions to the headwaters of Canterbury rivers. In 1863 he crossed the Southern Alps by what is now known as Haast Pass, and reached the West Coast. Haast produced the first systematic account of glaciers and mountains in the heart of the Southern Alps. He described his pioneering work in Canterbury in Geology of the provinces of Canterbury and Westland, New Zealand (1879).

James Hector in Otago

James Hector, a young Scottish geologist, was appointed provincial geologist in Otago in 1861 – the time of the discovery of gold at Gabriels Gully and the Otago gold rushes.

Hector was employed to draw up a geological map of the province. By September 1862 he had explored eastern Otago, and gathered 500 specimens of rocks, fossils and minerals. During 1863 he moved on to the West Coast, with a pioneering return trip from Dunedin to Milford Sound.

Using all the information available (including data from Hochstetter, Haast and others), Hector produced the first comprehensive geological map of New Zealand for the 1865 Industrial Exhibition held in Dunedin.

Footnotes
  1. Quoted in Peggy Burton, The New Zealand Geological Survey, 1865–1965. DSIR Information Series 52. Wellington: GSNZ, 1965. › Back

The New Zealand Geological Survey, 1865–1892

By 1865 there was a move to undertake a national geological survey, mostly so that central government could maintain control over discoveries of gold and coal. James Hector from Otago was approached for advice. Rather than simply reporting on mineral prospects, he proposed an organisation based on a museum that would study the natural sciences in New Zealand. As this was a much more ambitious project, it is surprising that it was accepted with little debate. It also started a national tradition of geology being regarded as a science, rather than part of mining as in many other countries.

Hector’s surveys, 1865–92

Hector was appointed director of the New Zealand Geological Survey and Colonial Museum in March 1865, at a salary of £800 per year. Over the next 25 years he and his staff explored most parts of New Zealand, and their reports were published in the annual Reports of Geological Exploration.

Doing double duty

To survey the entire country, James Hector was able to employ a clerk, a draughtsman, a chemist and a messenger – but no field staff. When Hector was out in the field all office work stopped, and when he was in the office the geological survey was suspended. Assistant geologists were later appointed.

Although Hector had prepared a geological map of the whole country in 1865, it was based on scanty information, and many large areas were unexplored. He sent his staff to examine places of economic or scientific importance, and gradually pieced together the geological jigsaw of New Zealand.

The top priority was to assist economic development. The public cry was ‘Find gold, find coal’. The first reports were mostly about mineral deposits, including the Thames goldfield, Taranaki oil seeps, and the Waikato coalfields.

Alexander McKay

All Hector’s assistants made important contributions, but the long-serving Scottish-born geologist Alexander McKay stands out because of the perceptiveness and reliability of his reports.

Being largely self-taught, McKay had not been biased by European concepts, and developed interpretations from his own observations. A major advance was his recognition that New Zealand mountains were not ancient, but had been uplifted in comparatively recent times (the last 10 million years), and were continuing to rise. He also deduced that there was a close relationship between earthquakes and faulting. He was possibly the first person in the world to recognise horizontal offsetting on a major fault.

Boxed fossils

Geologist Alexander McKay was employed to collect fossils, in order to date the rocks in different parts of the country. He made large collections, some of which have not been bettered. But they were not identified at the time and remained packed up in boxes for many years. They form the core of the national fossil collection, held at GNS Science.

Study and training

Because of the interest in gold and other minerals, geology was one of the first university subjects taught in New Zealand – at Canterbury and Otago by the late 1870s, followed by Auckland in 1883. In 1878 the Otago School of Mines offered university-level education for mining engineers. A network of mining schools gave practical training for people working in the mines.

Decline of the early geological survey

During the long depression of the 1880s Hector was able to resist financial cutbacks, but the Liberal government elected in 1891 was unsympathetic. In 1892 McKay was transferred to the Mines Department and the Geological Survey received no finance. Hector remained as director of the Colonial Museum, but responsibility for geology and mining was taken away from him.

Achievements

Between 1865 and 1892 Hector’s survey reported on the country’s major geological features and mineral deposits. Although small, New Zealand has an almost complete record of rocks from the Cambrian Period (about 540 million years ago) to the present day. By 1892 the complexity had been recognised, but many problems remained unresolved. The survey produced few detailed investigations and only rudimentary maps.


Mapping, volcanoes and geophysics: 1900–1965

J. M. Bell: detailed mapping

In 1904 a young Canadian geologist, James Macintosh Bell, became director of the Geological Survey, and applied the field experience he had gained in Canada. Whereas earlier geological surveys had been sketchy, Bell decided that detailed maps would have a scale of 1 inch to 1 mile (1: 63,360), with the aim of covering the whole country. No topographic maps were available, so surveyors were included in the field parties. As in North America, field work became a major expedition, with a large group (including field hands and a cook), camping equipment and supplies.

Although Bell only served from 1905 to 1911, he established a tradition of detailed mapping that lasted 50 years. But progress was slow, and staff were often transferred to economically productive projects.

Field work

The pattern of field work remained almost unchanged until the 1940s. Geologists spent five to seven months each year in the field, often under canvas. They worked every fine day, and were supposed to cover about 30 square miles a week. Evenings were spent plotting observations by lantern or candlelight. After financial cutbacks in the 1920s and 1930s, wives worked as cooks and camp organisers.

Most geologists used bicycles for transport, although a local farmer or transport service might be paid to help move camp. Winters were spent in Wellington, writing reports and preparing maps for publication.

Studying volcanoes

In 1920 Thomas Jaggar, director of the Hawaii Volcano Observatory, reported on the need for a volcanological observatory in New Zealand. As a consequence Leslie Grange made detailed maps of an enormous area between Rotorua and Mt Ruapehu. He became interested in the ash deposits of the region, where stock were suffering from a wasting condition called ‘bush sickness’. Grange and N. H. Taylor showed that ash from the Taupō and Kaharoa eruptions lay beneath the area. It was later recognised that the ash and pumice were deficient in the trace element cobalt. When this was added, animals thrived.

An economic focus: 1930s

In the late 1930s the government pushed to replace imports with local materials. Geological investigations focused on assisting the gold mining industry, and investigating coal resources and a steel industry.

With the outbreak of the Second World War, almost all geological work was aimed at replacing imports. This also brought scientific rewards. On an expedition to South Westland to locate mica (needed for radio capacitors), geologists Harold Wellman and Dick Willett recognised the Alpine Fault for the first time. Although this is a huge feature that bisects the South Island, it had been overlooked by scientists doing detailed mapping.

The birth of geophysics

Geological investigations had traditionally focused on rocks visible at the surface or tested by drilling. Geophysics was a method of working out the geology beneath the surface without actually touching the rocks. Introduced in the 1930s under the sponsorship of Ernest Marsden (secretary of the Department of Scientific and Industrial Research), geophysical techniques were used in New Zealand to explore for buried gold-bearing gravels and other underground mineral deposits. It was soon clear that geophysical prospecting saved time and could be used in identifying dam sites, underground water supply and a variety of engineering projects. A Geophysics Division of the department was set up in 1951.

A complete geological map

By 1955 only about one-third of the land area had been covered by geological maps, some of which were already obsolete. It was clear that the national geological survey, begun nearly 100 years earlier in 1865, would never be completed. Dick Willett, newly appointed as director of the Geological Survey, focused on a short-term project – a less detailed geological map of the whole country, at the scale of 4 miles to 1 inch (1:250,000), and concentrating new field work in places that were poorly known. Within 10 years, 28 maps were published. An up-to-date geological map of New Zealand was completed in 1965, in time for the 100th anniversary of the New Zealand Geological Survey.


Studying the sea floor and earthquakes

Remote sensing

Until the Second World War, geologists studied only the surface of the land. With new technology, they could study deeper rocks on land, and look beneath the sea. To do this they used various methods of remote sensing – seeing the rocks without touching them.

Shape of the sea floor

Detailed charting of the New Zealand coastline was completed by 1855, but there was little information on the shape of the sea floor, except for measurements in shallow water. For almost a century knowledge of the sea floor remained minimal, apart from scattered soundings that indicated widely varying depths. The continuous-recording echo-sounder, developed during the Second World War, meant that depth measurements could be gathered rapidly.

Interest in marine resources after the Second World War led to the establishment of the New Zealand Oceanographic Institute, a branch of the Department of Scientific and Industrial Research. One of the first jobs was collating bathymetric data (depth measurements) to determine the shape of the sea floor. A bathymetric map published in 1964 showed that beneath the sea, the land around New Zealand extended offshore to form an enormous continental margin, more than 10 times the land area above sea level. The new bathymetric map revealed that further offshore there was a pattern of submarine canyons, troughs, irregular slopes, and volcanic seamounts. It was found that the continental margin represented submerged continental crust that was likely to have rocks similar to those exposed on land.

Sedimentary basins

Although several oil seeps were known, exploration for hydrocarbons (which make up oil and other fossil fuels) was not successful in the 19th and early 20th centuries. In the early 1950s Shell BP Todd made seismic surveys in Taranaki, and the Kāpuni gas field was discovered. It was suspected that beneath the continental margin there were sedimentary basins that might contain oil and gas, but marine seismic surveys were required.

The Continental Shelf Act 1964 authorised offshore prospecting for petroleum, and in the succeeding decade most of the continental shelf was explored. As anticipated, sedimentary rocks were found to lie under much of the shallow continental margin. A number of distinct sedimentary basins have been recognised. Although the Māui gas field is the only offshore site so far exploited, several other oil and gas prospects are known in offshore Taranaki, and there is potential for further discoveries as more detailed exploration is undertaken.

Understanding earthquakes

Earthquakes were regarded as a curiosity in the first part of the 20th century. Between 1913 and 1926, the New Zealand Official Yearbook annually commented that ‘earthquakes are rather a matter of scientific interest than a subject for alarm’. Opinions changed after the damaging 1929 Murchison and 1931 Hawke’s Bay earthquakes, and a small government seismological network was set up.

Earthquake zones

As seismological methods for determining the epicentre of earthquakes improved worldwide, it became clear that earthquake activity was confined to narrow zones or belts. The circum-Pacific belt ran through New Zealand, and seismologist R. C. Hayes recognised that the shallower earthquakes occurred on the Pacific (eastern) side, while deeper earthquakes were further west.

Although there were ongoing arguments about the cause of earthquakes, by the 1950s there was evidence for an eastwards-sloping zone of earthquakes underneath the North Island, later named a Benioff zone. It was found that crust from the Pacific Ocean was being pushed (subducted) beneath the North Island, and that this was the cause of many of the deeper earthquakes.

Faults

Geologists have found that the New Zealand crust is splintered into a jigsaw of blocks, separated by cracks or fractures known as faults. Evidence from offset river terraces showed that some faults have moved repeatedly, causing large earthquakes. New Zealand scientists have become leaders in paleoseismology – the study of past earthquakes.


Plate tectonics and other advances

Plate tectonics

Before the late 1960s there was no unifying theory that explained the working of the earth and its surface features. Geology was mainly a descriptive, land-based science, and it was unclear how New Zealand was related to Australia and other countries of the Pacific.

Post-war exploration of the oceans provided a new view of the earth: the ocean floor is not as old as the continents. It lies on much younger volcanic rocks that have been ejected at mid-ocean ridges.

In the developing concept of plate tectonics, the surface of the earth was visualised as a mosaic of about 10 major crustal plates, moving independently but driven by convection currents deep within the earth.

Understanding the New Zealand region

The theory of plate tectonics was largely worked out and tested in the northern hemisphere. Understanding of the region around New Zealand had to await surveys of the sea floor, as well as the first deep- ocean drill holes in the region. A new picture became clear between 1969 and 1972.

The New Zealand region was originally on the margin of the Gondwana supercontinent, adjacent to Australia and Antarctica. New Zealand split away about 85 million years ago. Seafloor magnetic patterns show that the Tasman Sea gradually widened for about 25 million years, until spreading ceased about 60 million years ago.

All aboard

New Zealand has been compared to an ark, sailing away from Australia with a cargo of Gondwana plants and animals – including ratite birds (the ancestors of moa and kiwi), tuatara and forests with kauri, podocarps and beeches. These then evolved in isolation. Plate tectonics revolutionised our understanding of why New Zealand plants and animals are unique.

About 25 million years ago a major fracture developed, and the largely submerged New Zealand region lay across the boundary between the Pacific and Australian plates. As the plates rotated, the opposite sides of the Alpine Fault started to move apart, and features that were originally adjacent are now separated by 480 kilometres. Earthquakes, volcanism and mountain uplift are all caused by New Zealand’s position across these two plates.

Earth science as a career

Until the 1960s there were few jobs for geologists in New Zealand, and many graduates worked overseas. The number of local earth science graduates has steadily increased, and they are now employed in petroleum, coal and mineral exploration as well as in engineering geology and environmental science.

Traditionally geology has been a white, male-dominated profession, and until the 1970s there was debate about the moral aspects of women doing field work alongside men. In 2006 there are now roughly equal numbers of men and women studying geology at undergraduate level. Few Māori have undertaken a career in earth science, and this had not changed at the beginning of the 21st century.

Research in New Zealand

Because of its range of natural features, New Zealand has been regarded internationally as a natural laboratory for geological study – from glaciation to volcanology and paleontology. The number of scientific papers and monographs published is much greater than would be expected from the size of the earth-science community. In a 2003 survey, earth science was rated third out of 41 disciplines taught at New Zealand universities for the quality and productivity of research.

Organisational changes

In 1992 the Department of Scientific and Industrial Research (including the Geological Survey) was closed, and replaced by commercially focused crown research institutes. The Institute of Geological and Nuclear Sciences is responsible for land-based and some marine earth science, and a group from the National Institute of Water and Atmospheric Research studies offshore geology. Both organisations are involved in Ocean Survey 20/20, which aims for a comprehensive survey of New Zealand’s Exclusive Economic Zone by 2020.


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How to cite this page: Simon Nathan, 'Geological exploration', Te Ara - the Encyclopedia of New Zealand, http://www.TeAra.govt.nz/mi/geological-exploration/print (accessed 6 June 2020)

He kōrero nā Simon Nathan, i tāngia i te 12 Jun 2006