GEOLOGYMegan Hoare

THE SOUTHERN ALPS AND PLATE TECTONICS

DEFINITIONA scientific theory that there are very large sections of the Earth's crust, which move slowly around on the mantle. The plates movements cause seismic activity.

CAUSES OF PLATE TECTONICS

The plates on the Earths surface move because of the intense heat in the Earth’s core that causes molten rock in the mantle to move. It moves in a pattern called convection, which is when warm material rises, cools, and eventually sinks down. When the cooled material sinks down, it is warmed and rises again.

EFFECTS OF PLATE TECTONICS

• New Zealand is on top of the boundary between lots of tectonic plates which means it is affected in many ways.

• These cause earthquakes, which occur when tectonic plates rub together and volcanoes which are caused when subduction occurs.

• An example of New Zealand being affected by tectonic plates are the Southern Alps, they were formed when multiple plates converged and caused the mountains to rise. Some plates are still rising, however Gravity is pulling them down and weather is eroding them.

SCREE SLOPES IN THE SOUTH ISLAND

DEFINITION

The collection of rocks and debris at the base of cliffs, mountains or hills that have accumulated through a long period of time.

CAUSES OF SCREE SLOPESScree formation is commonly thought of as the reason to the formation of ice within mountain rock slopes. During the day, water flows in the discontinuities in the rock wall. If the temperature drops, for example with the beginning of evening, this water might freeze. Since water expands when it freezes, it generates forces that can either create new cracks or wedges blocks into an unstable position. Freeze-thaw scree production is thought to be most common during spring and autumn, when the temperatures fluctuate around 0°C.

EFFECTS OF SCREE SLOPES

• In New Zealand plants such as Willowherb and Drooping Poa live on scree slopes, and are the only places that they can survive.

• Animals like lizards and insects survive well on scree slopes.

• Scree slopes are good for providing entertainment for people. Some people go hiking on scree slopes, which can be quite dangerous, there is even an activity called "screeing", which is a lot like skiing, but without the snow and skis.

THE GLACIAL LAKES OF SOUTHLAND

DEFINITIONA glacial lake is a lake which was originally a glacier, that has melted. They are formed when a glacier erodes the land, and then melts, filling the hole or space that it was made.

CAUSES OF GLACIAL LAKES

Glacial lakes are caused when glacier melt, when a glacier is in one place for a while it starts to erode the land. They also occur when a glacier acts like a dam, to trap lots of water in a valley.

EFFECTS OF GLACIAL LAKES• Glacial lakes effect many things such as the

ecosystem, when a glacier moves over land it pulverises the minerals and when the lake is formed many sediments settle in the bottom, supporting a large population of algae and making the lakes appear green.

• There are many glacial lakes in the South Island, because it was an area that was covered with glaciers around 20,000 years ago.

EARTHQUAKES AND VOLCANOES IN THE NORTH

ISLAND

DEFINITION

Earthquakes: a sudden violent shaking of the ground, typically causing great destruction, as a result of movements within the earth's crust or volcanic action.

Volcanoes: a mountain or hill which has a crater through which lava, rock fragments and gas have been erupted from the earth's crust.

CAUSES OF EARTHQUAKESEarthquakes are usually caused when multiple tectonic plates converge, rub or interact in a sudden way, this causes vibrations and the earth to break apart and create fault lines.

CAUSES OF VOLCANOES

Volcanoes are caused when two tectonic plates diverge, and hot magma rises to the surface of the earth, which causes bubbles of gas to appear in it. This gas causes pressure to build up in the mountain, and it eventually explodes.

EFFECTS OF EARTHQUAKES

Earthquakes and aftershocks can cause shaking, which can make buildings fall over,not only does this cause lots of destruction, it also causes massive issues, like the earthquake in Napier in 1931, which killed 256 people. The local landscape changed drastically, such as the sea bed becoming dry land.

EFFECTS OF VOLCANOES

Volcanoes cause a lot of destruction, they can destroy whole cities or completely bury them with molten rock. This happened in the Mount Tarawers eruption in 1886, this explosion caused a pyroclastic which destroyed several villages and the Pink and White Terraces. The effects of the ash in the air were observed as far as Christchurch, which is over 800km South.