Science, Rocks

Question 1

Formation of sedimentary rocks

Answer 1

1. Eroded or weathered sediments broken off larger rocks end up in the water and begin to settle (sedimentation)
2. With time, more layers pile up and presses down the lower layers (compaction)
3. More layers (strata) and further compaction forces out water from the layers
4. Salt crystals glue the layers together (cementation)

Question 2

Examples of sedimentary rocks

Answer 2

• Sandstone
• Limestone

Question 3

Properties of sedimentary rocks

Answer 3

• Crystalline sedimentary rocks - composed of crystals
• Horizontal layers (strata)
• Contain fossils
• Hardness: medium - very strong
• Density: less dense

Question 4

Formation of metamorphic rocks

Answer 4

• Formed from sedimentary rocks
• High temperatures (closer to mantle)
• High pressures (lots of sediment piled on top of the rock)

High temperatures/pressures —> rock is metamorphisized

Question 5

Examples of metamorphic rocks

Answer 5

• Phyllite
• Gneiss
• Marble

Question 6

Properties of metamorphic rocks

Answer 6

• Crystals: size increases, as grade of metamorphic rock increases
• Harder than sedimentary (harder as grade increases)
• Some small layers

Question 7

Formation of igneous rocks

Answer 7

• Formed from metamorphic rocks
  1. Metamorphic rock melts and forms magma
  2. Hot magma cools either above surface or below
  - Intrusive: Underground, slowly uplifted to the surface
  - Extrusive: Above surface, volcanoes

Question 8

Examples of igneous rocks

Answer 8

• Diorite
• Granite
• Obsidian

Question 9

Properties of igneous rocks

Answer 9

• Crystals: crystalline
• No fossils
• No layers
• Hard
• Weather-proof

Question 10

Formation of fossils: Fossilization Process

Answer 10

1. Animal is buried by sediment and soft parts decay
2. More sediment builds up and is compressed to form rock
3. Minerals in the ground water replace the bone forming a fossil
4. The rock rises to the surface and is worn away by erosion

Question 11

Difference between magma and lava

Answer 11

Magma - Molten rock that is underground
Lava - Molten rock that breaks through the earth’s surface

Question 12

Extrusive vs intrusive igneous rocks

Answer 12

Extrusive:
- Appear on surface
- Cool down via surface
- Formed from lava
- Cooling, solidifying

Intrusive:
- Beneath the surface
- Cool down beneath the surface far enough away form heat
- Formed from magma

Question 13

Crystals in extrusive vs intrusive igneous rocks

Answer 13

Extrusive:
- Small crystals because quick cooling time
- Crystals do not have lots of time to grow

Intrusive:
- Big crystals because rock is given time to grow crystals