GEOL120 Flashcards
(57 cards)
What are some types of Volcanic Rock?
Gabbro, Diorite, and Granite are all plutonic Volcanic rock.
What are some other types of Volcanic Rock?
Trachyte
Dacite
Komatiite
Tuff
Ignimbrite
Kimberlite
Explain the volcanic rock Trachyte?
Trachyte is a volcanic product of parent magma differentiation
Explain Dacite?
It’s the volcanic equivalent to Granodiorite, and formed by subduction of early oceanic crust, under thick felsic continental plate.
Explain Komatiite
It’s the volcanic equivalent to Peridotite
Oldest ultramafic magmatic rocks (~3.4 GA)
Spinifex bladed Acicular olivine and pyroxene in fine matrix
Explain what a Tuff and Ignimbrite is?
Explain Kimberlite
Ultramafic mantle-derived material brought to the surface by kimerblite pipes, Dykes, Sills.
Brecciated (rubble/broken fragments)
Brings up diamonds from depths via several emplacement models.
Economically viable Kimberlites tend to occur on Precambrian and Archaean Cratons.
What does a Ancient Kimberlite Volcano look like?
What is a Hypabyssal Rock?
Rocks that have intruded at shallow depths and characteristics between plutonic and igneous rocks. It’s grain size is typically 1 mm.
What’s the difference between Hypabyssal and Subvolcanic?
They’re the same.
What are some Hypabyssal rocks?
Regarding Volacanism and Plate tectonics, what are three main ways to produce a magma?
Decompression melting
Flux Melting
Increasing temperature
(All methods are controlled by the tectonic environment)
A map of Volcanism and plate tectonics
Explain Basaltic Volcanism?
It’s the most common form of volcanism on earth,
Occurs in a wide range of tectonic environments such as:
- MOR’s
- Island/volcanic Arcs
- Intraplate Volcanoe’s
What are Submarine eruptions? And what percentage of the earth do they cover?
They are a product of Ridge Volcanism in the Mid Ocean ridge, and they cover for 70% of earth’s surface.
They develop along fissures, parallel to the ridge.
What happens in a Submarine eruption?
Hot Mantle rock rises to shallow depths and undergoes decompression melting-
Basaltic lava cools quickly underwater and forms pillows-
Circulation of seawater in the crust creates hydrothermal vents, convection - circulating “black smokers” and temperature, where unique organisms and sea life live in abundence.
What is does this picture represent?
An outcrop or formation of pillowing from a submarine eruption,
Due to their pillowing and sausage shapes this tells us they were formed underwater.
Desribe the shield volcano of the “Hawaiin” volcanism
The large broad shield volcanoes are due to their thin low viscosity basaltic lava flow.
Emitt very little pyroclastic material during eruptions.
They have a steady production of lava fountaining and are considered the safest of volcanoes.
What does this picture represent?
The different types of volcanoes, and the diagrams that represent their structure or size relative to one another.
What is a hot spot and how does it form?
There are two types of hot spots:
- Oceanic hot spots:
Large Igneous provinces are?
Enormous sheets of low viscosity basaltic magma continue to be erupted over long timescales producing a basltic plateau.
Developed by a mantle plume beneath an are that is undergoing rifitng.
They are usually basaltic but compose a diverse range of composition.
Frequently assosciated with extinction periods eg Siberian Traps - Permian ex
What are Columnar Basalt’s?
It’s a basalt that commonly breaks into regular columns because of contraction when cooling.
This indiccates subaerial cooling.
Exactly, what types of formation is this?
Culumnar Basalt.
What can you share about Andesitic and Rhyolitic volcanism?
- It’s more viscous than basalt lava and do not folw as easily.
- Andesitic volcanism commonly associated with subduction but not all.
