Week 4 - Earth Materials

Question 1

Why are framework silicates stable?

Answer 1

Each silica is sharing its oxygen with another silica atom, making more bonds, the stronger structure is stable.

Made up of one silica (Si4+) and four oxygens (O)
Have a tetrahedral shape, meaning that they can polymerase.

Individual tetrahedra may be polymerized by sharing oxygen atoms between tetrahedra e.g.
rings, chains, sheets, frameworks

Question 2

What binds minerals in igneous rocks together?

Answer 2

Silicate minerals are bound by tetrahedral structures

Question 3

What is a felsic rock?

Answer 3

• felsic mineral (light colour, low density) e.g. feldspar, quartz

Question 4

What is a mafic rock?

Answer 4

• mafic mineral (dark colour, high density) e.g. mica sheets, pyroxenes (single chains), Olivines (isolated tetrahedra)

Question 5

What is the difference between contact and regional metamorphic processes?

Question 6

Is the rock cycle a true cycle?

Why is it important ?

Answer 6

Yes

Question 7

What are the rock forming minerals?

Answer 7

Silica (Si)
Oxygen (O)
Aluminium (Al)
Iron (Fe) 
Calcium (Ca) 
Sodium (Na) 
Potassium (K) 
Magnesium (Mg)

Question 8

List the 3 broad classes of rocks

Answer 8

1. Igneous rocks - formed by solidification of magma - can be extrusive and intrusive
2. Sedimentary rocks - aggregates deposited by transporting medium such as water, wind or ice; deposits of organic origin; chemical properties
3. Metamorphic rocks - describe change in mineral assemblage and textures due to elevated temperatures and pressure

Question 9

What are the implications for these Earth Materials on the landscape?

Question 10

What are the differences between Minerals and Rocks?

Answer 10

Minerals - naturally occurring inorganic chemical compounds’ having a specific internal structure and regular chemical composition

Rocks - are natural mixture or aggregates of minerals

Question 11

What is a Mineral?

Answer 11

• Mostly crystaline
• Have specific physical properties which reflect both their composition and atomic structure and affect rate of weathering
• silicates are the most common minerals (make up 95% of Earths crust)

Question 12

Describe Silicates

Answer 12

Made up of one silica (Si4+) and four oxygens (O)
Have a tetrahedral shape, meaning that they can polymerase.

Individual tetrahedra may be polymerized by sharing oxygen atoms between tetrahedra e.g.
rings, chains, sheets, frameworks

Question 13

What is an Igneous Rock?

What is it made up of?

Answer 13

1. Igneous rocks - formed by solidification of magma, can be..
   Extrusive (volcanic) - cool rapidly at Earth’s surface, fine crystal grain size
   Intrusive (plutonic) - crystallise deep below the surface and cool slowly, coarse grain size
2. Mostly made of silicate minerals
   - felsic mineral (light colour, low density) e.g. feldspar, quartz
   - mafic mineral (dark colour, high density) e.g. mica sheets, pyroxenes (single chains), Olivines (isolated tetrahedra)

Question 14

Intrusive Rock Structures

Answer 14

Structures when they solidify under the surface:

• Batholiths - largest
• Dykes - vertical structures, magma solidified in fractures
• Sills - horizontal sheets of solidified magma

Question 15

What is the origin of magma?

Answer 15

Basalt Magma - generated from partial melting of ultramafic rocks in the asthenosphere

Granite Magma - generated from partial melting of rocks in lower crust

Question 16

What are Sedimentary rocks?
List the minerals
List the 3 types

Answer 16

Sedimentary rocks - aggregates deposited by transporting medium such as water, wind or ice; deposits of organic origin; chemical properties. *often form in layers or strata

Common minerals:
Quartz - stable and weathering resistant
Clays - formed by weathering feldspar
Carbonates - formed as shells or preciptates

1. Clastic - fragments of clasts/rocks and mineral particles from weathering and erosion (separated based on particle size) e.g. sandstone, mudstone
2. Chemical - material carried in solution is precipitated (evaporation) e.g. rock salt
3. Organic - accumulated remains of plants and animals e.g. limestone

Question 17

What are Metamorphic rocks?

Answer 17

Metamorphic rocks - formed from preexisting rocks that have been altered by external forces - describe change in mineral assemblage and textures due to elevated temperatures and pressure

• have recrystallised in solid state due to changed physical conditions
• have internal planar structure called ‘foliation’due to alignment micas
• materials mainly silicates
• from metamorphism of sedimentary rocks include slate, schist, gneiss

Question 18

What is Dissolution?

Question 19

What is Oxidation?

Question 20

What is Hydrolysis?

Question 21

What is Relief? Slope? Aspect? Topography?

Answer 21

Relief - the difference between the highest and lowest point

Slope - relief/run

Aspect - direction of the slope, you tell by the way you are facing the slope

Topographic position - you draw a line along the map, highest point on that line