Download What are Tectonic Plates?

Geological History
Of New Zealand
Presented By Jamie Hrstich
Plate Tectonics and the
Southern Alps
What are Tectonic Plates?
The Earth’s lithosphere, the crust or
the outermost shell, is broken up into
what we call tectonic plates. These
plates are known for their large scale
motion, forming different landscapes
through reaction with each-other.
Tectonic plates are scientifically known
for the concept of the early continental
drift that separated the different areas
of Pangea, the original continent. With
the Earth’s lithosphere consisting of
many major and minor plates, each
relative motion that is created between
several plates is determined by the type
of plate boundary e.g. divergent,
convergent and transform. Formations
such as earthquakes, mountain ranges,
volcanoes and oceanic ravines occur
commonly during the contact or movement
between plates. The leading theory of
plate movement is though to be driven by
Plate Tectonics and the
Southern Alps
The History Behind The
Southern Alps
Running 500km from north to south in the
South Island Of New Zealand is a vast
mountain range called the Southern Alps
or Kā Tiritiri o te Moana in Maori. This
dramatic geological feature was formed
by the collison of the south east
Pacific Plate and the north west IndoAustralian plate. In the last 45 million
years, the tectonic pressure created by
the transform boundary of the two plates
has pushed 20km of rock up to form the
Alps, although most of it has been
eroded. In the recent 5 million years,
uplift is continuing at a faster speed
along the Alpine Fault, creating recent
earthquakes such as the incident in
Christchurch 2010. As of today there are
16 points in the Southern Alps that
exceed 3,000 metres in height, excluding
the tallest point at 3,724 metres also
known as Mount Cook.
Plate Tectonics and the
Southern Alps
Types of Plate Boundaries
Divergent Boundaries: A divergent
boundary is created by two tectonic
plates slide apart or away from each
other. Formed by seafloor-spreading, the
continent splits created an ocean basin
and allowing for new plate area to cause
Convergent Boundaries: Either forming a
subduction zone or a continental
collision, convergent boundaries occur
when two plates slide towards each other,
with one eventually sliding under the
other. As this happens, the downward
plate sub ducts into the asthenosphere,
melting and creating magma which then
rises to create volcanoes.
Transform Boundaries: Transform
boundaries are created when two plates
slide against each other along a
transform fault. Strong earthquakes can
be caused during this process however no
Plate Tectonics and the
Southern Alps
The Impact the Southern Alps
has on New Zealand
The Southern Alps is one of the major
highlights of the South Island in New
Zealand as it’s magnificent heights and
length makes it a popular tourist
attraction. With beautiful snow and
scenery, the Southern Alps offer the
perfect
climbing expedition and a great trip for
tourists who want to see more of New
Zealand. Alongside this, the cold
climates that these peaks reach up to
have a natural effect on New Zealand as
well. Clean and fresh water that is
caught from the peaks runs down the
mountains and into our fresh streams and
local water bodies. Natural vegetation
grows as well, however this is
threatened by introducing animals such
as the red deer and the chamois.
Various national parks across the
mountain range protect the mountains
from these animals inhabiting. Although
the Southern Alps create less room for
us to build whilst keeping the climate
cold, it is a well known treasure to our
nation.
Scree Slopes in the
South Island
What are Scree Slopes?
A scree or a scree slope is a collection
of rock debris that has been accumulated
at the base of cliffs, mountains and
volcanoes due to periodic rockfall. This
debris forms a slope at the bottom of a
mountain, differentiating depending on
amount of debris and rock size. The
formation of scree slopes results from
several methods of rock decay, including
chemical and mechanical weathering. The
different formations of a scree slope
can depend largely on the location of
the natural structure, as temperature,
climate, amount of rainfall and many
other aspects can depends on which
method of rock decay will act upon it.
Most scree formation is commonly
attributed to the creation of ice inside
crevices on mountain rock slopes, hence
mechanical weathering. Rainwater
manages to travel into these cracks and
over a cold period of time, the water
Scree Slopes in the
South Island
The Impact That Scree Slopes
Have On New Zealand
Landslides such as these can effect
anything surrounding it’s area. To
humans, scree slopes are dangerous and
depending on the rock size that occurs
in the creation of the debris can be
considered dangerous. For buildings,
roads and people near the edges of these
cliffs or mountains can be in harm’s way
when it comes to falling rocks and it
may harm people or create large problems
for the government to handle. Not only
this, scree slopes can prevent plantlife
from growing and with a strong enough
slide, they can even conceal a glacier.
Especially around autumn and spring,
scree formation can occur frequently due
to the fluctuating warm and cold
temperatures. Although they may be a
great sight to see on a hiking trip,
they can be dangerous and a nuisance to
us, animals and the environment.
The Glacial Lakes Of
Southland
What are Glacial Lakes?
Glacial lakes are the origins of
glaciers, the melted water that fills
the area that the glacier originally
eroded. In the last glacial period,
which was around 10,000 years ago,
glaciers began to retreat (a retreating
glacier often left large pieces of ice
behind). After this period of ice age,
these pieces and glaciers melted to
create the lakes. To erode the ground
around it, the ice of a glacier would
pulverize the minerals of rocks by
scouring, moving over the rocks and
crushing them. By doing this, glaciers
created holes and gaps between drumlins
and hills. When they melted into the
lakes we know today, the pulverized
sediments that contains minerals such as
iron, phosphorus, and boron. There are
different types of glacial lakes such as
proglacial and subglacial however almost
every lake in the South Island, such as
The Glacial Lakes Of
Southland
The Impact the Glacial Lakes
have on Southland
Moving glaciers that scrape the ground
like sandpaper tend to carry some of the
minerals that they crush when they
created large holes in the ground. By
doing this, the glaciers may have had a
large impact on the environment. By
moving minerals to other areas in the
early days, the minerals may have
fertilized into the soil and created
better ground for farming and fruit
growth. This may be the reason why the
soil in the South Island is rich and
good for farming animals and crop.
Sediments of minerals that are found at
the bottom of the lake could be taken
and used for human purposes. Glacial
lakes can like other natural beauties be
tourist attractions and can create a
place for scenic views and activities
such as fishing, kayaking, boat cruises
and jetboating. Glacial lakes can also
Earthquakes and
Volcanoes in the North
Island
What are Earthquakes?
An earthquake is the shaking of the surface
on the Earth and the outcome of the energy
released from the movement of tectonic
plates on a fault line. Earthquakes usually
if formed in oceans can create tsunami
whilst creating volcanic activity and
landslides onshore. The severity of the
shaking can toss people around and can
destroy buildings, structures and even
whole cities. Seismic waves are the sudden
waves that are released by the energy
created at the focus (or hypocentre) of the
fault line. Seismic activity refers to the
frequency, type and the size of earthquakes
experienced. The magnitude of an earthquake
is identified as the intensity of the
earthquake and how much damage it inflicts.
This intensity is measured through either a
Richter scale or a Mercalli intensity
scale. Earthquakes with a magnitude of 3 or
under are considered as weak and almost
imperceptible whereas magnitude 7 or higher
Earthquakes and
Volcanoes in the North
Island
What are Volcanoes?
A volcano is a cone-shaped mountain
formed by the geological outcome of
magma and lava that has been released
through a crack or a fault in the
earth’s crust. Volcanoes are rupture
points of the earth’s surface that
allows hot lava, volcanic ash and gases
to escape from the magma in the earth’s
upper mantle. The mountains that are
formed are created by tectonic plates
mainly diverging or converging. As seen
on the top left, the volcano forms from
the pressure creating when a plate sub
ducts in a converging zone, breaking
apart as it enters the earth’s upper
mantle. This create more magma and is
pushed through the lithosphere and the
continental crust to form a volcano.
There are different types of volcanoes
such as cinder cones, caldera volcanoes
and shield volcanoes, all of which are
Earthquakes and
Volcanoes in the North
Island
The Impact That Natural
Disasters Have on the North
Island
Volcanic and seismic activity have
affected our awareness, our tourism and
our environment. The fact that in the
history of New Zealand we have suffered
the eruptions and rumbles of earthquakes
has raised our concerns as to
whether it will happen again and whether
it is safe enough to live next to an
active volcano. Campaigns have to this
day kept us on the edge of our seats to
prepare ourselves for when another
devastating event occurs. Alongside
this, the activity underground has
helped us to developed our energy and
our tourism. The geothermal activity in
Taupo and our mud pools and geysers have
created great tourist attractions for
people around the world and citizens of
New Zealand to visit. Earthquakes and
volcanoes can also cost us a lot of
money as eruption or occurrence of these
can destroy our environment which can
ruin our infrastructure and can cost us
more development.