Geology

Question 1

What is an extrusive igneous rock? Examples.

Answer 1

A rock formed when hot magma is ejected to Earth’s surface. Lava cools down rapidly and becomes solid as fine grained crystals.
Ryolite, basalt

Question 2

intrusive igneous rock
examples

Answer 2

Hot magma cools slowly down an solidifies beneath the upper surface and builds coarse-grained crystals
granite, gabbro, dolerite

Question 3

formation of a sedimentary rocks

Answer 3

Particles of organic matter are transported by wind or water. These sediments originated through physical or chemical processes or through accumulation of organic remains. Material is deposited, buried, compacted and transformed—> lithification

Question 4

Sedimentary rocks
Mechanical process

Answer 4

most common
Weathering or erosion transforms existing rocks into mineral particles
Transport by wind, rain or floating water into large water basin, deposited in layers as sediment, accumulate, buried compacted by the weight above

Shale, sandstone

Question 5

Sedimentary rocks
Organic matter

Answer 5

Organic matters from animals and plants derived from organic decomposition
Limestone (skeletons, shells, corals)
Coal (wood, plant debris, spores, algae)

Question 6

Metamorphic rock

Answer 6

High temperature or pressure for a long period of time, minerals can change dramatically and alter the character of a rock.
Recrystallisation under influence of temperature and/or pressure, without melting.
Limestone—>marble

Question 7

Granite

Answer 7

Intrusive igneous rock
Rounded, hilly areas
Rocky slopes and outcrop
Resistant to weathering
Acidic , nutrient- poor soil
Pale, coarse- grained, sandy
Large-leaved plants (Bushwillow species, Maryland)

Question 8

Basalt

Answer 8

Extrusive igneous rock
Flat plains with patches of damp clay which forms pans
Relatively rapid weathered
Alkaline and nutrient rich soil
Dark colored, fine grained, clayey
Small-leaved trees (Acacias)

Question 9

Intrusive igneous rocks- examples

Answer 9

Gabbro- coarse-grained
Granite- coarse-grained
Dolerite- medium-grained

Question 10

Extrusive igneous rocks
Examples

Answer 10

Ryolite- fine-grained, glassy
Basalt- very fine-grained

Question 11

Sedimentary rocks
Examples

Answer 11

Dolomite- fine to coarse
Sandstone- medium- grained
Shale- fine-grained
—> mechanical
Limestone- fine to coarse
—> organic

Question 12

Metamorphic rocks
Examples

Answer 12

Marble- medium to coarse
Gneiss- medium to coarse
Slate- fine

Question 13

Crust

Answer 13

7-35 km
Solid
Magnesium, aluminium silicates

Question 14

Mantle

Answer 14

2900km
Solid or plastic
Iron rich
Heat leads to large scale convection current

Question 15

Spheres of crust and mantle

Answer 15

Lithosphere- 100km, Earth’s crust upper part of mantle, solid,floats on asthenosphere, up to 1000degrees

Asthenosphere-100km, plastic, molton, causes tectonic movement, up to 1500•C

Mesosphere- more solid

Question 16

Outer core

Answer 16

2300km, dense liquid, iron- nickel, 5000•C
electricity conducting layer that combined with Earth’s rotation initiates a dynamo effect—> electrical current—> Earth’s magnetic field

Question 17

Inner Core

Answer 17

Immense force of gravity,
Solid, iron, nickel, 5500•C

Question 18

Mechanical weathering

Answer 18

Gradual break down of a rocks:
-thermal variations
-pressure released
-water absorbed by chemicals in the rock and pressure increases
-salt crystals accumulate in crevices when water evaporates, temperature rises, pressure increases
-wind blowing
-biotic (animal walking, plants growing)

Question 19

chemical weathering

Answer 19

-water combined with chemicals on surface
-water combines with iron minerals in the rock (rusting, oxidation)
—> breaking down adhesive properties
-lichen absorb chemicals
- root associated fungi break down minerals in rocks, available nutrients for plants

Question 20

Erosion

Answer 20

active movement of rock particles
water & wind

Question 21

Erosion / Weathering in Bots

Answer 21

Weathered and eroded material from western mountains of Southern Africa deposited into Kalahari basin.
Massive blanket of sand is flat and has little gradient. For this reason there is little visible weathering and erosion in most of Botswana.
Southern east regions have most exposed geology and most rapid erosion.

Question 22

Why is the biodiversity of the Okavango limited?

Answer 22

Delta is dominated by Kalahari sand with small patches of alluvial soils. Leached of nutrients over millions of years.
Lack of topographical relief (hills, mountains).
Retains less water, good filtration
Very uniform, nutrient poor soil of sand results in poor plant diversity and carrying capacity.

Kalahari Apple-leaf
Silver Cluster-leaf
Camel thorn
Three-awn grasses (poor grazing grasses)

Question 23

catchment area

Answer 23

Entire area of land that a river drains.

Question 24

watershed

Answer 24

Decides one catchment area from another

Question 25

3 main zones of a river

Answer 25

upper reaches:
- mountains area
- fast flowing
- low sediment load

middle reaches:
- slow moving
- more sediment

lower reaches:
- wide, slow-flowing, meandering
- much higher sediment load

Question 26

Rivers of Northern Botswana

Answer 26

Highlands of Angola/ watershed :

KWANDO RIVER
-south to Linyanty Marsh
-blocked by Linyanti Fault line
-forced northeast along Linyanti River into Chobe River
-meets Zambezi

CUITO AND CUBANGO RIVER
-from Benguela Plateau/ Angola
south into northern Botswana to the Delta

Question 27

Describe the process of weathering

Answer 27

Weathering means the gradual breakdown of rocks through mechanical or chemical agents like water, plants and atmosphere.

Question 28

Erosion

Answer 28

-the active movement of rock particles by wind or water
-link between weathering and depositing

Question 29

Fault-lines of Botswana

Answer 29

1 Pan Handl Fault
2 Linyanti Fault
3 Gumare Fault
4 Kunyere Fault
5 Thamalakane Fault
6 Zimbabwe Kalahari Axis
7 Bakalahari Schwelle