GEOGRAPHY ALTERNATIVE ASSIGNMENT
EXPLORING VULCANICITY
A BRIEF EXPLANATIONÂ
ON THE TWO TYPES OF VOLCANOES
Stratovolcanoes The sides of the volcano are concave in an upward direction, with a steeper top and gentler bottom. The body is made up of layers of lava, ash and fragmented material. There is a large depression on the top, known as a caldera. Magma flows through the volcano through the vents; there is the main vent in the centre of the volcano reaching to the top, and secondary vents which branch out from the main vent reaching to the side surfaces.
Shield Volcanoes Unlike stratovolcanoes, shield volcanoes have sides that are convex in shape and gently sloping. As a result, the volcano has a broad summit and the volcano covers quite a wide region. Shield volcanoes barely have secondary vents, but a somewhat wide main vent that extends from the magma chamber. Like stratovolcanoes, the body of shield volcanoes are composed of layers, but for this volcano the layers are mostly made up of solidified lava formed through gentle lava eruptions.
MATERIALS USED FLOUR + WATER DOUGH
a cheaper alternative to clay (covers the sides of the volcanoes) which depicts the shape of the volcanic cones well
NEWSPAPER makes up the insides of the model to make it lighter and not waste flour. We also want to use recycled material as much as possible.
FOOLSCAP CARDBOARD
a readily available material and a sturdy base for the model (also recycled material)
TOILET PAPER ROLL
a cylinder shaped material, perfect for the vent of the volcanoes( wich is also a recycled material)
PAINT
just a small touch to make the model more realistic and to distinguish the different parts of the volcano.
SMALL PLASTIC CONTAINERS
steady for holding up the first layer (which is also a recycled material)
RED PLASTIC BAG
a sort of flow-like material that resembles the magma coming from the mantle
COTTON
We use cotton as it is easy to find and is easily shaped to resemble the pyroclastic flow that comes out of the vent.
a summary
THE DESIGN OF BOTH VOLCANOES
OUR OBJECTIVES We need our models to be representatives of the real volcanoes, in terms of structure and their key features. We did intensive research so that we can get accurate data. We collated a bunch of pictures as reference for the construction of the model. Two layers need to be made because one of the key differences of the volcanoes is where they are formed (at what plate boundaries they are most commonly found). The materials need to be as accessible and cheap as possible, but the quality shouldn't be compromised. We did trials to make sure the final volcano is sturdy enough and will not collapse. Time was also a factor in the design. We needed to design as fast as possible because of the possibility of Home-Based Learning (HBL) preventing us from meeting and working together. We constructed the model before the circuit breaker period and the model only needed to be painted and made more realistic.Â
THE GENERAL DESIGN When designing the model, we had a few things in our mind. Firstly, the shapes of the volcanoes are different, which means we can't use a stencil of sorts to make both volcanoes. So, we decided to find clay-like material so that the volcanoes can be moulded by hand and we can shape it as whatever we want. Secondly, the distance between the first and the second layers cannot be that huge and the support needs to be strong so that it can hold on to the weight of the flour on the first layer. For this, we decided to use small plastic containers found in grocery stores and strong adhesives to make sure the model is stable. Thirdly some features that are the same in both volcanoes need to be represented by the same material, such as the usage of toilet paper roll for the vents on both designs. Lastly, both volcanoes have different features and need different material and/or techniques to be made. The unique features of the volcanoes will be described in detail in the following pages.
STRATOVOLCANO special features
LAVA FLOW We created long strings of flour and attached it to the upper part of the stratovolcano to show the lava flow, we wanted to show lava flow on this model and not on the shield volcano because this volcano have a more explosive eruption and therefore the lava flow is obviously seen, unlike the shield volcano model, whose eruptions are only shown by sparks of bright colours (going to be shown later).
LAYER OF LAVA + PYROCLAST Stratovolcanoes are made up of layers of lava and pyroclast interchangeably, so we decided to stick out layers of newspaper to give us a texture that imitates the pyroclast (which contains rock fragments and ash). We use the black colour so that it contrasts clearly with the brown and imitates the colour of ash.
SUBDUCTION Since the stratovolcano is located in convergence boundaries where subduction occurs, we need to create a feature that resembles a denser plate subducting under a less dense one.
SECONDARY CONE When the vent becomes blocked, the magma is forced to find a new exit route, hence a secondary cone is formed. Secondary cones can also be present in shield volcanoes, but it is more commonly associated with stratovolcanoes so we chose to show it in the stratovolcano model, we cut up our excess toilet paper roll for its vent and made the secondary cone with more dough.
MAGMA CHAMBER The magma from the subduction rises up and creates a magma chamber. Since a chamber is like a space, we decided to cover one of our plastic containers with red tape to represent a chamber of lava, right underneath the vent.
SHIELD VOLCANO special features
LAYERS OF LAVA Since the layer of ash and lava are not that different, we feel like we need to highlight another feature on this volcano, which is the ageing feature, the layer of lava is younger at the top than at the bottom, this is shown by the gradation of colour from the bottom to the top going form dark to light.
FREQUENT ERUPTIONS Since the eruptions of the shield volcano are more frequent and happens in a smaller rate, we decided to present a shield volcano when it is erupting, but the size of the lava flow needs to be reduced tremendously if compared to the stratovolcano, hence the eruption is only shown by sparks of bright red and orange here and there
MAGMA FROM MANTLE lava from the shield volcano have low viscosity level . That means that the lava is less viscous, that is why we represented the magma with those of the more thinner material, red plastic bag
SEPARATION OF PLATES Shield volcanoes are commonly located in divergence boundaries, we created plate movement diagrams to show how the plate separates and the magma rises from the middle and fill the gap between the plates as they move apart.