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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.