Week 4: Volcanism Flashcards
Name the 2 types of origins for surface processes
1) Endogenic: Involves internal force originating from below the Earth’s surface
2) Exogenic: Involves external force originating from within the Earth’s atmosphere
Describe the process of differentiation for Earth
- Early Earth kept molten by collisions, compression, and radioactivity
- Energies from collisions and compression dissipates, causing Earth to cool down to iron’s MP
- Heavier elements such as iron then sinks to the centre, while lighter elements such as silica float to the surface
- Iron then solidifies and coalesce to form a core
Describe the composition of Earth
- Inner core of solid iron at 7000C
- Outer core of Iron/ Nickel, which convects to create geodynamo/ magnetic field
- Mantle made up of ductile solid rocks
- Lithosphere made up of liquid aesthenosphere and solid silicate crust
Name 3 types of crust and their properties
1) Primary crust:
- Made of lighter elements that rose through the magma ocean during differentiation
- High crater density
2) Secondary crust:
- Made of recycled material from mantle convection and volcanism
- Low crater density - smooth crust with volcanoes and largely basaltic
3) Tertiary crust:
- Formed by tectonic plates movements
Name 3 types of volcanism and their properties
1) Spreading center volcanism:
- Occurs at oceanic ridges where 2 plates diverge. As plates are pulled apart, the aesthenosphere rises up to fill the void, then decompresses and melts to form basaltic magma.
2) Subduction zone volcanism:
- Occurs where 2 plates converge. Commonly found in the “ring of fire”.
- Descending plate bends downwards, forming oceanic trench.
3) Intraplate volcanism:
- Occurs at hotspots within the plate’s interior. The hotspots are underlain by plume of hot mantle.
Name 4 types of volcanoes and describe their features
1) Cinder cones:
- Built from blobs of congealed lava
- As lava solidifies when blown into the air, it falls down as cinders
- Circular/ oval cones, bowl-shaped crater, single vent
2) Stratovolcano:
- Built from alternating layers of lava, volcanic ashes, and cinders
- Solidified lava forms dikes to strengthen the volcano
- Steep symmetrical cones, crater or multiple vents
3) Shield volcano:
- Built from accretion of fluid lava flow
- Broad and gentle slopes
4) Lava domes:
- Bult from small bulbous lava masses that are too viscous to flow far
- Grows by internal expansion
Give the process and evidences of volcanism on the Moon
Process: Only due to partial mantle heating
Evidences:
1) Mare: Lunar maria have lower crater density than the highlands - implies that lunar maria was formed via volcanism that smoothens out the crust by flooding the lower regions of the highlands with lava
2) Sinous Rilles: Lava channels in luna maria
3) Dark mantling deposits: Small spheres of orange/ black glass. Formed during eruption when gas bubbles burst near the surface.
Give the process and evidences of volcanism on Mercury
Process: Major volcanic activity stopped after Mercury cooled. This is because cooling causes Mercury to shrink, forming a seal which prevents lava from reaching the surface.
Evidences:
1) Pyroclastic ashes
Give the process and evidences of volcanism on Venus
Process: Dominated by features related to mantle plumes - Intraplate volcanism
Evidences:
1) Coronae: Dome-shaped feature of the crust which forms when plumes of rising mantle push the crust upwards. This dome then collapse at the center, allowing magma to leak out the sides.
2) Pancake domes: Broad and flat profiles formed from viscous lava with surface covered in cracks and faults
3) Infrared radiation: Shows some flow are warmer, and therefore more recent, then the surrounding rocks
4) SO2 gas: Sulphuric clouds enveloping the planet can’t persist without replenishment from volcanism
Give the process and evidences of volcanism on Mars
Processes:
- Mostly intraplate volcanism
- Contains 4 large shield volcanoes: Ascraeus Mons, Paronis Mons, Arsia Mons, Olympus Mons
Evidences:
1) Cerberus Fossae: Mars’ surface contains many cracks and are prone to quakes
- Suggests that mantle is pushing on the crust form below
- Some cracks also have a dark streak of pyroxenes alongside it, which are commonly found in lava
Give the process and evidences of volcanism on Io
Processes: Volcanism powered by tides
Evidences:
1) Sulphur allotropes dominates surface colours
2) Low crater density - must have a replenishment process
