Second Batch: 2.2-2.7 Flashcards
2.1: About the North Antrim Coast:
- Predominantly rocky coastline
- History of volcanism - slow cooling of molten basalt erupted 60 million years ago has preserved softer sedimentary rocks underneath
- Subsequently covered by ice sheets during Quaternary
2.1: About Igneous:
- Very slow rate of erosion
- Igneous rocks are crystalline; interlocking crystals make for strong, hard erosion-resistant rock
- Have few joints so there are limited weaknesses to be exploited by erosion
2.1: Types of Igneous rocks:
Granite
Basalt
Dolerite
2.1: About Metamorphic:
- Slow rate of erosion
- Crystalline
Many metamorphic rocks experience foliation:
– When crystals are oriented in 1 direction allowing for some weaknesses - These rocks are often folded and fractured
2.1: Types of Metamorphic rocks:
Slate
Schist
Marble
2.1: About Sedimentary:
- Moderate to fast rate of erosion
- Most sedimentary rocks are clastic and erode faster than crystalline rocks
- Younger sedimentary rocks tend to be weaker
2.1: What does it mean to be clastic?:
As being composed of consolidated sediments formed by the accumulation for fragments derived from pre-existing rocks
2.1: Why are ancient sedimentary rocks more resistant to erosion?
They have been compressed and compacted over millions of years and so are significantly more resistant
2.1: How can permeability affect rock strength?
- Permeability is important as groundwater can weaken rocks
- It can lead to high pore water pressures reducing stability
2.1: Define permeability?
A rock that allows water to pass through it
2.2: What is the structure of rock?
- The arrangement of rock and its bedding planes
- Determines strength and surface area exposed to waves/ subaerial erosion
2.2: Define jointing:
Cracks/ fracture present in layers/ body of rock
2.2: Define dipping:
Which way a column of rock leans:
- Seaward
- Landward
2.2: Define faulting:
Fracture or zone of fractures between 2 blocks of rock
2.2: Define folding:
Stack of originally level surfaces that are bent or curved during permanent deformation
2.2: Stability of different cliff dips:
Seaward dip is typically more unstable than a landward dip
2.2: Define colonnade and entablature:
Entablature is layer of rock that sits above the colonnade
- Entablature is made of laterite and is more permeable
- Colonnade consists of basalt columns with joints present horizontally and vertically
2.2: What about entablature overhanging?
- When water reaches overhanging entablature, it causes it to become saturated
- So heavier
- Some water can escape into colonnade leading to further breakdown
- Most water stays in the entablature which leads to mass movement of it
- It topples down
2.2: How can extrusive igneous basalt rock be formed?
When volcanic lava flows over ground
2.2: How can intrusive igneous basalt rock be formed?
Through volcanic lava funnelled through tunnels
2.4: Describe the process of cave/arch/stack/stump:
- Starts with headland
- Causes waves to refract
- Erosion concentrated in weak points on side of headland
- Hydraulic action/ abrasion causes caves to form on sides
- Caves meet forming tunnel
- Tunnel becomes arch which increases in size
- Top of arch collapses leaving stack
- Waves erode and cut into base of stack
- Stack becomes unstable collapses
- Leaves a stump, submerged at high tide
2.5: Describe areas dominated by marine erosional processes:
- Often at headland sites
- Wave cut notch and platform formation
- Rate of erosion varies over time
- Steep face
2.5: Describe areas dominated by sub-aerial erosional processes:
- Often at backshore of bays
- Refractions means lower marine energy
- Cliff degradation increases from above
- Curved slope profile
2.6: What are the 3 main types of sub-aerial processes?
Mass Movement
Rock Breakdown:
- Mechanical
- Biological
- Chemical
2.6: Example of biological weathering:
Molluscs
2.6: Example of chemical weathering:
- Chemical Reactions
- Seaweed Acid
2.6: Example of mechanical weathering:
- Frost shattering & Freeze Thaw
- Salt Crystallisation
2.6: How do Frost Shattering & Freeze Thaw contribute to rock breakdown?
- Temp has to change daily - expansion and contraction of rocks
- During Freeze-Thaw, water seeps into cracks, freezes and expands by 9%
- Rock is left angular, cliff face would be jagged and material would accumulate at bottom as scree slope
2.6: How does Salt Crystallisation contribute to rock breakdown?
- Waves break and splash water against cliff
- Water evaporates, leaving sodium and magnesium behind
- Once they’re in cracks and joints, the salt crystal grow
- Exerting pressure and force the rock apart
2.6: How does Oxidation contribute to rock breakdown?
- Chemical reactions via iron minerals in rock
- Leaves red-orange rusty colour
- Rock crumbles away
2.6: How does Carbonation contribute to rock breakdown?
- Slow dissolution of limestone due to rainfall
2.6: How does Hydrolysis contribute to rock breakdown?
- Minerals breakdown to form new clay minerals, and new materials in solution
- Due to water/ dissolved CO2
2.6: How does Seaweed Acid contribute to rock breakdown?
- Have sulphuric acid, so if cells break, it can lead to rock being dissolved
- Rock minerals aren’t bonded together so rock crumbles
2.6: How do Molluscs contribute to rock breakdown?
- Live on rocks and scape away to get food
- Leaves hole in the rock
- Holes become weak points for weathering to act
2.7: Define Hydraulic Action:
Force of water hitting cliffs and squeezing air into cracks in the rock
2.7: Define Abrasion:
Force of bits of rock carried in the water blasting off the cliff
2.7: Define Attrition:
Process of rocks hitting each other and breaking into smaller rocks
2.7: Define Corrosion:
Chemical reaction between sea water and minerals in the rocks
