lecture 2

Question 1

1. What Hawaii consist of?
2. These islands sit in the middle of which tectonic plate?

Answer 1

1. It consists of multiple VOLCANIC ISLANDS very far from any PLATE BOUNDARIES.
2. The Pacific Plate

Question 2

1. What is plume?
2. What do mantle plumes consist of?
3. Why is the magma extremely hot?

Answer 2

1. Spreading out in the shape of a feather
2. MANTLE PLUMES consist of extremely hot MAGMA originating at the CORE-MANTLE boundary
3. Because The CORE heats the MAGMA that slowly gets pumped into the MANTLE, rising it
   up towards the LITHOSPHERE.

Question 3

1. How can it escape the core and go to the lithosphere?
2. What does it melt?
3. After that there are 2 possibilities what are they?
4. What are we observing in the Hawaiian Islands?

Answer 3

1. Because its extremely high temperature, it can melt its way through the MANTLE and towards the LITHOSPHERE
2. The head of the MANTLE PLUME spreads out (like a mushroom) just below the LITHOSPHERE, melting surrounding UPPER MANTLE rock.
3. Possibility 1: MAGMA can gradually cool beneath the surface, creating lots of volcanic rock (known as IGNEOUS ROCK).
   Possibility 2: The HOT SPOT (i.e., MAGMA beneath the surface) causes a volcanic eruption. Such volcanoes are known as HOT SPOT VOLCANOES as they are fed by the pool of HOT MAGMA just below the surface.
4. Possibility 2

Question 4

1. Why do we observe this trail of islands and not just one huge volcanic island?
2. What is the name of the future island?

Answer 4

1. Given that MANTLE PLUME originates below the LITHOSPHERE, its position remains fixed and is NOT affected by the moving TECTONIC PLATE above it.
2. Loihi, now referred to as Kama’ehuakanaloa

Question 5

1. What do the volcanoes above HOT SPOTS, as we encounter in Hawaii look like?
2. What are those types of volcanoes known to be?

Answer 5

1. The composition of the magma is a very fluid so there is far less risk=eruptions are less violent because it is far from any plate boundaries, thus the magma has far less silica= less sticky. Less silica also means less gases.
2. Shield volcanoes

Question 6

Give examples of shield volcanoes.

Answer 6

Mount Karthala, Piton de la fournaise and mount terror

Question 7

1. Where does the mantle plumes originate from?
2. These mantle plumes feed what to shield volcanoes above hot spots?
3. There would be less what than is encountered at subduction zones.
4. What does silica consist of?

Answer 7

1. At the core-mantle
2. Hot magma above hot spots
3. the magma may contain some silica and aluminium from the mantle rock.
4. Silicon and Oxygen (SiO2)-the deeper you go the less abundant these become (with aluminium)

Question 8

1. What does lava form when it solidifies?
2. What floor does this rock make up?

Answer 8

1. form DENSE BASALTIC ROCK (i.e., BASALT)
2. BASALTIC ROCK due to all the volcanic activity in oceans

Question 9

1. How do SHIELD VOLCANOES look?
2. What are their characteristics?
3. What is a caldera?

Answer 9

1. From above, like an Ancient Greek shield. That’s where that name comes from!
2. -wide DOME (the circular mound that sticks out of the ground) with a gradual slope (not steep like STRATOVOLCANOES).
   -wide dome consists of MANY LAVA
   layers
3. a CALDERA may form (not always) when
   surrounding stone collapses into hole/space that once contained molten stone (MAGMA) released as LAVA during an eruption

Question 10

1. What does the silica makes this magma?
2. What rock does lava that solidifies from?

Answer 10

1. It makes it thicker, sticker and more resistant to flow.
2. This LAVA solidifies to form a variety of rocks, with most common being ANDESITE.
   ANDESITE is named after ANDES mountains and is 52 – 63% by weight SILICA

Question 11

How do STRATOVOLCANOES look?

Answer 11

narrower DOME (the circular mound that sticks out of the
ground) with a steeper slope

Question 12

1. What are cinder cones?
2. What is a PYROCLASTIC ROCK?
3. What do we refer to as very small PYROCLASTIC MATERIALS (i.e., fragments less than 2 mm in size)

Answer 12

1. CINDER CONES are tiny (generally less than 400 m tall), steep volcanoes made up of PYROCLASTIC ROCKS such as SCORIA.
   CINDER CONES are often referred to as SCORIA CONES
2. PYRO = Greek for FIRE
   CLASTIC = broken
   rocks generated by volcanic activity and that consist of fragments of other rocks and minerals
3. ASH

Question 13

1. What are lava domes (volcanic domes)?
2. What is special about its lava?
3. Where are they found?

Answer 13

1. They are very small volcanoes that possess extremely viscous (extremely
   thick) MAGMA and LAVA.
2. The LAVA does not move far at all and continues to pile up just outside the volcano’s vent (i.e., hole).
3. LAVE DOMES are often found next to larger STRATOVOLCANOES.

Question 13

1. What is scoria?
2. How are cinder cone eruptions?
3. Does scoria fly far from the volcano’s vent (hole) and what shape does it give to the cinder cones?

Answer 13

1. They are bits of LAVA that harden in midair after being ejected by a volcano’s gases
2. They are violent, ejecting molten PYROCLASTIC materials (such as SCORIA) into the air
3. No and it makes it have a steep in shape