ACHIEVEMENT STANDARD Earth and Space Science 2.3 as Worth 4 credits Examplar written by Logan Coleman

Introduction This assessment activity requires you to study the Taupo Volcanic Zone in the centre of the North Island and the formation of rocks in this volcanic zone. You are to research and produce a report, a pamphlet, poster or a PowerPoint presentation to help visitors to the area understand the formation of two or more rocks found in the Taupo Volcanic Zone. You will be assessed on the depth and comprehensiveness of your report, pamphlet, poster or PowerPoint presentation.

Tasks Using the resources your teacher has provided, begin researching the Taupo Volcanic Zone. Select two or more rocks found in the Taupo Volcanic Zone and create a report, a pamphlet, poster or a PowerPoint presentation that includes the following aspects for each rock. Describe how it is formed. Include the type of rock that it is. Explain in depth how the rock has been formed. To explain: – relate the formation of the selected rock to the relevant stage(s) of the rock cycle – relate the selected rock found in the Taupo Volcanic Zone to the geological history of the Taupo Volcanic Zone – link the type of magma found in the area of the Taupo Volcanic Zone to the formation of your selected rock. Explain in depth how the rock has been formed by linking the magma type of the relevant volcano, to the formation of the selected rock giving reasons for the formation. Make links between the formation of the selected rock to the relevant stage of the rock cycle and the geological history of the Taupo Volcanic Zone. Explain in depth how the features of the Taupo Volcanic Zone are weathered and eroded to produce the final shapes we see today.

AUCKLAND VOLCANIC FIELD

INFORMATION The Auckland volcanic field consists of around 50 volcanoes It occupies an area of 360km 2 The metropolis of Auckland, New Zealand’s largest city is built upon this volcanic field There are a variety of different shape volcanoes which have all been formed from basaltic magma It is a monogenetic volcanic field (also known as a hotspot) as the magma does not come from a chamber but instead comes directly from the mantle

YOUNGEST VOLCANO The youngest volcano is Rangitoto that erupted from the Waitemata Harbour around 600 years ago The island has a diameter of 5.5km and is made up dark basalt rocks that have formed from basaltic magma, it was once quarried for scoria Rangitoto is a shield shaped volcano

OLDEST VOLCANO The oldest volcano is thought to be Lake Pupuke on the North Shore It is estimated to have been created around 250,000 years ago Lake Pupuke consists of a scoria tuff ring surrounding 2 craters which have filled with water known as a maar Like the rest of the Auckland volcanoes it is formed from basaltic magma, it reacted violently with the ground water creating a huge pyroclastic explosion

MY TWO ROCK TYPES 2 rock types that can be seen in the Auckland Volcanic field are Basalt Scoria

MAGMA TYPE All magma is the result of plate tectonic movement and subduction and melting of convergent plates Basaltic magma has a high iron (Fe) and magnesium (Mg) content Basaltic magma has a low viscosity due to the low silica content As it is a low viscosity this usually means that the eruptions are not as violent as the stickier magma like andesite and rhyolite. This means that it flows easily and can basaltic lava flows can cover large distances before hardening, this is evident in Meola reef and the lava flows along Motions Rd

BASALT

Basalt is an igneous rock Igneous rocks are formed from cooling magma (intrusive) or cooling lava (extrusive It is formed from the slow cooling of basaltic lava so it is an extrusive igneous rock Basalt is usually black or dark grey in colour due to the high iron and magnesium content Basalt may be slightly red/brown in colour as the iron in the basalt reacts with the air (oxidises) It may contain a small amount (percentage) of vesicles which signify that dissolved gases have escaped from the cooling lava

WEATHERING AND EROSION Basalt is a hard and dense rock It is not affected much by normal weathering such as wind and rain Weather will tend to smooth the rock down and wear away rough edges This is evident in comparing the lava flows from Rangitoto (600 yrs old) that are sharp and jagged to the lava flows from Lake Pupuke (250,000yrs old) that are smooth and more rounded

WEATHERING AND EROSION Basalt can be eroded gradually by wave action This is evident in tidal zones such as the lava flows from Lake Pupuke at Takapuna Boat Ramp

SCORIA Scoria is an igneous rock Igneous rocks are formed from cooling magma (intrusive) or cooling lava (extrusive It is formed from the rapid cooling of basaltic lava so it is an extrusive igneous rock Scoria can range from black or dark grey to red due to the high iron and magnesium content Red scoria occurs when the iron in the scoria reacts with the air (oxidises) Scoria contain a high amount (percentage) of vesicles which signify that dissolved gases (carbon dioxide and water) have escaped from the cooling lava Scoria is formed form the basaltic magma that is erupted and cools quickly in the air

WEATHERING AND EROSION Scoria is a crumbly and low density rock It is affected greatly by normal weathering such as wind and rain Weather will tend to break scoria down into very small pieces (to an almost sand-like consistency) Examples of finely ground red scoria can be seen around the Auckland volcanoes

BIBLIOGRAPHY Volcanoes of Auckland: The Essential Guide by Bruce Hayward and Graeme Murdoch and Gordon Maitland