Now and Beyond, the Future of New Zealand

The New Zealand of today has an abundance of notable geographic forms and processes.  As a portion of the subcontinent Zealandia, the islands currently lay atop a convergence zone between the Pacific and Australian plates.  On North Island, subduction of the oceanic Pacific plate has played a major role in earthquakes and volcanic land forms such as volcanoes.  From these volcanoes ash, tephra and lava have created rich andisol soils resulting in fertile farmland and prosperous agricultural trade for New Zealanders.  On South Island, the continental-continental convergence beneath the Alpine Fault both formed and continues to uplift the Southern Alps approximately 7mm per year.  Consequently this mountain range acts as a major barrier to the prevailing westerly winds, creating orographic lift, adiabatic cooling and leaving the leeward side of the mountains much drier.  An important variable for weathering on the islands is their maritime tropical (mT) climate which has plentiful moisture and warm temperatures.  

Map of Subduction Zones and Fault Lines in New Zealand
Here we can see the convergence of the Pacific Plate under the Australian in
the north, the Australian underneath the Pacific in the south and Alpine Fault  inbetween.
Image courtesy of: http://www.otago.ac.nz/geology/research

Satellite Image of New Zealand, Plate Boundaries and Interaction Included
This dynamic view shows the oceanic boundaries in blue and continental in red
with volcanoes in red triangles and earthquakes in orange.
Image Courtesy of: http://modernsurvivalblog.com/earthquakes

New Zealand in 2022 (+10 yrs)

In only a decade, changes to New Zealand's geography will occur, however they will not be as extreme as changes 100 or 1000 years into the future.  The islands are a coastal landscape surrounded by ocean waves and subject to frequent tropical cyclones, therefore the coastline of New Zealand will recede in many places and wave cut formations will grow.  In 10 years we could see at least 1 devastating storm as well as multiple smaller systems.  During a cyclone a combination of raised sea levels, intense rainfall, and 100+ mph winds would batter the shores.   The resulting floods would be a strong catalyst for erosion, creating powerful inland currents heavy with sediment and debris.  Although the global climate is currently in an interglacial warming period the temperature increase in 10 years would be minimal and sea level rise will be insignificant.  

A Storm Surge on Wellington Coast Breaks through a Seawall (1972) 
A scenario like this is likely to happen again when the next large Cyclone strikes,
perhaps in the next ten years.
Image Courtesy of:  http://www.teara.govt.nz/en/coastal-erosion/3/5

New Zealand in 2112 (+100 yrs)

After a century there will be opportunities for less frequent geological events to occur. The Taupo Volcanic Zone is one of the most active volcanic sites in the world with Mt. Ruapehu at the center.   Being a stratovolcano of andesitic composition and having had a last major eruption in 1995 it is possible that a larger eruption of 100+ year frequency will occur.  Due to the higher levels of felsic or viscous material present the build up of heat, gases and pressure will result in a violent eruption.  Perhaps the greatest danger to the population is the abundance of snow and ice in the current caldera.  After a large eruption melts all the snow and ice, fast moving, dense and destructive lahars will form and race down the mountainside.  If the eruption is uneven and not directly upwards Mt. Ruapehu will jettison a pyroclatic flow of hot ash and tephra even faster towards the cities of North Island.  

A Violent Eruption of Mt. Ruapehu with Resort in the Foreground  (1995)
Characteristic of andesitic volcanoes, another major eruption could repeat or surpass
the magnitude of this one in the next century.

Image Courtesy of:http://www.prints.co.nz/page/fine-art/PROD/8351

 

New Zealand in 3012 (+1,000 yrs)

On a geographic timeline 1,000 years has more potential for altering the landscape of New Zealand. The Pacific and Australian plates themselves will have shifted 50-100 meters.  This means the Southern Alps will have risen over 30 meters and the width of South Island will have decreased as the western continental mass converges with the eastern.  North Island will have increased in mass as the continued subduction of the Pacific plate melts the continental crust into rising magma eventually emerging as lava through extrusive processes such as volcanoes.  The global temperature will rise several degrees celcius resulting in melted glaciers and sea level increase. Higher seas will cause a steep decrease in coastline and land area.  Many of New Zealand's over 3,000 glaciers will recede because the amount of ablation due to melting will be greater than accumulation.  This will leave glacial land forms such as deep u shaped valleys, erratics and large moraines.  

Image of a Hanging Valley In New Zealand
Many more glacial features like hanging valleys will be common around the
Southern Alps after the glaciers recede.   Note the wide U shape formed from a large glacier

Image Courtesy of:http://glaciers1011r1.wikispaces.com/Hanging+Valley

 

In conclusion it comes as no surprise to see such dramatic changes to New Zealand in the future.  The islands fall into the categories of coastal, glacial and even fluvial, all of which bring elements of weathering and deposition.  Another final factor to equate is the future effects of humans on the landscape.  From anthropogenic land repurposing to the complete decimation of native flora due to the farmland cultivation, humans will have a profound effect on New Zealand after 10, 100, or 1000 years.  

Figure Comparing Native Forest Coverage Before and After Polynesian Settlement
The Maori were a 3rd world culture with only fire as a tool to clear forests.  
Imagine the impact after 1,000 years of modern industrial logging techniques.
Image Courtesy of:http://envirohistorynz.com/2009/12/

Bibliography:

Dr. Casey Allen

http://www.otago.ac.nz/geology/research/structural_geology/alpinefault/index.html 

http://hypertextbook.com/facts/ZhenHuang.shtml 

http://modernsurvivalblog.com/earthquakes/another-quake-rocks-christchurch-new-zealand/

http://www.teara.govt.nz/en/coastal-erosion/3/5 

The Skies of New Zealand

 New Zealand is located under a maritime tropical air mass (mT).  This indicates abundant precipitation and relatively warm temperatures due to mid-latitudes and its close proximity with the Pacific Ocean.  The warmer sub-tropical air results in a higher saturation quantity and therefore higher specific humidity.  However, using a hygrometer we would find some sharp variations in humidity between the coastal regions and colder southern mountain ranges. 

Map of Annual Rainfall in New Zealand
Note the contrast in rainfall  in the south Island
and the resulting rain shadow to the East of the mountains.
Image courstesy of:
 http://www.niwa.co.nz/education-and-training 

Map of Mean Temperature in New Zealand
Being in the Southern Hemisphere temperatures
approach sub-tropical in the North Island, and cooler
temperate in the South Island.
Image courtesy of:
http://www.niwa.co.nz/education-and-training

 Another major factor in New Zealand's climate is the interaction between the persistent Westerly winds and the 10,000ft plus mountains that span it's length.  As the saturated air over the Tasman Sea is forced East it collides with the windward side of the mountains.  This results in an adiabatic process called Orographic Lifting where the air moves upwards to the peak of the mountains.  The higher elevation cools the air due to lower pressure and quickly raises the relative humidity to 100% as it passes the Lifting Condensation Level, resulting in precipitation.  When the winds reach the eastern or leeward side of the Southern Alps they are much drier and are commonly known as foehn winds.  Because much of the remaining water vapor evaporates as the foehns reach the lowlands, the land is left dry and arid in the south east. 

Effective Visualization of Orographic Lifting
Thanks to our professor we can see the essential properties of an Adiabatic Process.
Image Courtesy of: Dr. Casey Allen

Graph of Annual Precipitation versus Distance Inland
from the West Coast of the South Island
Note the majority of rainfall takes place before crossing the highest peak.
Also note the steep drop in precipitation on the eastern side of the mountains.  
Image Courtesy of: 
http://www.briangwilliams.com/weather-climate/orographic-precipitation.html

   New Zealand  experiences its summer months from November to Februrary.  Excess latent heat from higher levels of Summer insolation contribute to high winds, low pressure cells and Cyclogenesis.  Tropical Cyclones are the most devastating of storms to hit New Zealand, commonly originating in the warmer equatorial waters to the North. 

Satellite Image of Cyclone Bola, 1988

Formed in the maritime equatorial (mE) waters near Fiji at the north of the image,

 Bola moved Southward changing from a Tropical to Extra-tropical Cyclone.

Image courtesy of:http://en.wikipedia.org/wiki/Cyclone_Bola 

 

 

The combination of warm tropical sea surface temperatures near Fiji, plentiful water vapor and an ideal latitude of 16-18 degrees south of the equator helped create Cyclone Bola on Feb. 23rd, 1988.  When a cold front from the Westerly winds penetrated a warm front from the South Trade winds an Occluded front was formed.  This resulted in much lower pressures at the convergence of the two fronts and the warm air and water from the north fueled Bola's development. 

 

Map of Cyclone Bola's Path From Fiji to New Zealand

 

 

 

The blue represents the early stages as well as the transition to an Extra-Tropical Cyclone. 

The yellow is Bola's Tropical Cyclone period as well as first land fall in Fiji.

Image Courtesy of:http://en.wikipedia.org/wiki/Cyclone_Bola

After reaching its peak power as a Tropical Cyclone, Bola devastated more than 3,000 homes and destroyed multiple bridges in Fiji before weakening on its way to New Zealand.  When it reached the North Island it dropped a record 917mm of rain over just a few days resulting in heavy floods.  The storm damaged roads causing 3 deaths and left thousands out of power due to downed power lines.   In all it was the most expensive recovery effort in New Zealand's history at over 160 million dollars in damage.

Sources:

 http://en.wikipedia.org/wiki/Cyclone_Bola

http://www.new-zealand-nz.net/weather.html

Dr. Casey Allen

http://weatherwatch.co.nz/

Erosion, Hydrology and Soil in New Zealand

 Over a third of New Zealand's fresh water is found in groundwater and derived from deep aquifers.  These aquifers are a permeable layer of rock located between two impermeable layers or aquicludes.  When a hole is drilled beyond the top aquiclude, the sealed pressure is released resulting in a naturally flowing artesian well.  The recharging or refilling of these aquifers takes place in the higher mountain ranges such as the Southern Alps of the South Island.  The source of water being rainfall or influent streams 

An Artesian Well in Marlborough, NZ located on the northern tip of the South Island.  As a reliable source of water , wells like these enabled early communities to  survive in dry regions.
(Image courtesy of http://www.marlborough.govt.nz/Environment/Groundwater.aspx )


Due to New Zeland's heavy dependence on agricultural exports, farmers were forced to clear forests even on the slopes near the mountains.  With over 22 hectares of plowed farmland this equated to the depletion of nearly 65% of original forestry.  New Zealand's regional podzolization resulted in deep sub soils with a thin top soil and abundant leaf litter.  With the absence of deep rooted Podocarp trees, biogenic transport accelerated and thus destabilized the soil.   This lowered the cation exchange capacity of the soil and left the grasslands infertile. 

Map of Erosion Susceptible Regions in New Zealand.  It is important to note the  greater weakness to erosion along  steeper slopes due to stronger gravitational impact. 
 (Image courtesy of http://www.seafriends.org.nz/enviro/soil/soilnz.htm)

Aerial view of dark green forest, light green man made pasture and the pale green areas spotted with bare soil.  The lack of stable roots and healthy top soil resulted in the creep and biogenic transport of soil down into gullies and rivers.  (Image courtesy of http://www.teara.govt.nz/en/natural-environment/4/1)
 

Map of Soil Orders of the North Island.  Unlike the South Island, notice the large presence of pumice soil as a result of volcanic ash from the Taoupo Volcanic Zone.  
 (Image Coutesy of http://www.mfe.govt.nz)

New Zealand's climate ranges from humid subtropical in the north to cooler more seasonal temperatures with frequent rain in the south. These conditions helped to form Inceptisols, Spodosols, and Ultisols, the three most common orders of soil in New Zealand.  Inceptisol is found along the flood plains east of the Southern Alps.  Spodosol is found around forested or previously forested areas.  This is due to the higher acidity from semi-coniferous leaf litter and the consistent rainfall  that leaches minerals from the O horizon. Ultisol is similar to Oxisol in its high weathering and red coloration.  It is found on the warmer North Island.     

 
Map of Soil Orders of the South Island.  The majority of the South Island is covered with spodosols formed by pedzolization.  (Image Courtesy of http://www.mfe.govt.nz)

Sources:

 Dr. Casey Allen 

www.mfe.govt.nz, 

www.teara.govt.nz,   

www.soils.landcareresearch.co.nz

www.waternz.org.nz

Formation of New Zealand

Zealandia's Full Underwater Expanse (google.com/images)

The land masses we know today as the islands of New Zealand happen to be at the highest elevation of a greater microcontinent known as Zealandia.  Once a part of the super continent Gondwana, Zealandia separated over 70 million years ago as a result of shifting circulations in the earths asthenosphere.  Under the supercontinent, new flows of molten rock moved outward and pulled the land apart.  The lowland rift between Zealandia and its former motherland filled with ocean, forming the Tasman Sea.  After millions of years of sea floor spreading as well as the cooling of the continent,  Zealandia was nearly entirely submerged beneath the waves.  

New Zealand's Tectonic Turmoil (google.com/images)

Picturesque enough to star in movies such as The Lord of the Rings and The Chronicles of Narnia, these islands also find themselves atop two tectonic plates, and three different kinds of  plate boundaries.  The North Island is the more actively volcanic of the two due to the subduction zone off it's east coast where the Pacific Plate sinks underneath the Australian Plate.  The grinding and heating between the two plates has resulted in the Taupo Volcanic Zone which includes the largest active volcano Mt. Ruapehu among many other composite or stratovolcanoes.  

A Calm Mt. Ruapehu (theencyclopediaofnewzealand.com)

Mt Ruapehu 1995 Eruption (tera.gov)

The major eruption in 1995 resulted in fast moving lahars, a combination of mud and volcanic ash that mixed  with the emptied crater lake water and melted snow.  Although the ash affected some livestock and a nearby hydro electric power plant, there were no casualties reported.  Without a dense population nearby, the 1945  eruption also had little direct impact on New Zealanders.  However the eruption blocked off the lower drainage point of the lake with tephra or pyroclastic material.  After the lake had refilled by 1953 the weaker tephra broke free, releasing a devastating lahar that compromised a railway bridge causing 151 deaths known as the Tangiwai disaster. 

Wreckage From The Tangiwai Disaster (google.com/images)

Introduction

Salutations! My name is Kevin McBride and the island nation of New Zealand will be the focus of my geographical analysis for this blog. 

Satellite Image of New Zealand

Why New Zealand? Other than the richly unique  landscapes and biodiversity, these islands happen to be a hotbed of geographic activity.  From top to bottom this corner of the world offers various different features, greatly due to its position atop a  subduction zone.  It is this process along with many others that result in the forms of towering mountains, glaciers and even one of the worlds largest super volcanoes.  I aim to investigate the native geography of New Zealand further and hope to shed some light on this mysterious island.