Physical Geography: Folding

• Core Unit 1 focuses on physical geography, specifically folding, faulting, and rocks.

Folding

• The bending of stratified rocks in Earth's crust results in folding.
• Deformation, such as bending, squeezing, stretching, or breaking, changes the original rock structure.

Parts of a Fold

• Anticline: The top part of a fold.
• Syncline: The down part of a fold.
• Limb: The sides of a fold.

Forces

• Compression: When a body of rock is squeezed together, it results in folding, which occurs at destructive plate boundaries.
• Tension: When a body of rock is stretched, it results in faulting, which occurs at constructive plate boundaries.
• Shearing: When rocks slide past each other, it results in faulting, which occurs at conservative plate boundaries.

Types of Folds

• Simple Fold: A fold where both limbs have the same slope.
• Asymmetric Fold: A fold where one limb's slope is steeper than the other limb.
• Overfold: A fold where the limb of one slope has been partly overturned on the other limb.
• Overthrust Fold: A fold where one limb completely overturns the other limb.

Folding Periods

• Caledonian Folding occurred 400 million years ago with a Northeast to Southwest trend, exemplified by the Wicklow Mountains.
• Armorican Folding occurred 250 million years ago with a West to East trend, exemplified by the Comeragh Mountains.
• Alpine Folding occurred 60 million years ago, forming the Alps Mountains.
• Alpine fold mountains are the highest today, while the Caledonian and Armorican mountains were once higher but have been worn down due to denudation.

Faulting

• A crack in the Earth's crust is considered faulting.

Types of Faults

• Normal Fault: Results from tension, pulling plates apart with vertical movement, exemplified by Rift Valleys (e.g., East African Rift Valley).
• Reverse Fault: Results from compression, with one block of rock forced upwards vertically over another, exemplified by Black Mountains.
• Thrust Fault: Results from compression, with vertical movement like a reverse fault, exemplified by Vosges, France.
• Tear Fault: Results from shearing, with horizontal movement as plates slide past each other, exemplified by the San Andreas Fault in California.

Rock Characteristics

• Minerals: Different minerals make up different rocks.
• Hardness: Depends on how strongly the rocks are cemented together.
• Color: Depends on the mineral content of the rock.
• Structure: Some rocks have layers (strata), while others are a solid mass.
• Texture: Depends on the size, shape, and arrangement of mineral grains.

Rock Groups

• Igneous: Rocks are formed when molten magma cools and solidifies above or below the crust.
• Sedimentary: Rocks are formed from the compression and cementation of sediment remains at the bottom of the ocean.
• Metamorphic: The minerals of existing rocks are changed through great heat and/or pressure.

Formation of Igneous Rocks

• Formed from the cooling of hot magma above or below Earth's crust.
• Magma rises due to lower density and pressure, melting crustal rock as it rises, and has temperatures exceeding 1200 degrees Celsius.
• Mainly found at destructive and constructive plate boundaries, allowing magma to escape through faults and fissures.
• Cooling speed affects crystal size; quick cooling results in small crystals (e.g., basalt), while slow cooling results in large crystals (e.g., granite).
• Can be intrusive (plutonic) or extrusive, depending on where the magma/lava cools.
• Intrusive rocks cool beneath the Earth's crust, while extrusive rocks cool above the Earth's surface.
• Granite is an intrusive rock, while basalt is an extrusive rock.
• Granite is composed of mica, feldspar, and quartz, with varying proportions creating different colors and textures.
• Example- the Leinster Batholith, formed during the Caledonian folding movement 400 million years ago.

Sedimentary Rocks

• These are formed when sediments at the ocean bottom are compressed, compacted, and cemented together naturally.
• Sediments consist of tiny rock fragments, sand, clay, and remains of plants and animals.
• Compaction and cementation make up lithification.
• Rocks usually laid in strata with defined bedding planes.
• Organic: Compacted remains of plants and animals (e.g., limestone).
• Inorganic: Compacted remains of pre-existing rock fragments (e.g., sandstone).
• Chemical: Sediments are compacted due to mud and sand.
• Limestone: Vertical lines of weakness formed when the rock was compressed.
• Bedding planes: Horizontal cracks between layers of sedimentary rock.
• Limestone slowly chemically weathers via carbonation from rainwater.
• Irish limestone formed over 300 million years ago.

Metamorphic Rocks

• Once igneous or sedimentary, changed physically and chemically by heat or pressure.
• Thermal Metamorphism: Rock changes due to great heat.
• Regional Metamorphism: Rock changes because of great heat and/or pressure.
• Process: The change from a older rock into a new and different rock
• New minerals form, texture changes, old minerals change shape, size and arrangement.
• Thermal metamorphism occurs at 250-850 degrees Celsius.
• Marble is formed from limestone.
• Dynamic metamorphism occurs when pieces of crust slip past each other.

Geothermal Energy in Iceland

• Derived from Earth's core heat, powering 32% of Iceland's electricity.
• Position on the mid-Atlantic ridge enables geothermal use for electricity and heating.
• Five geothermal power plants provide hot water for 98% of Iceland's housing.
• Magma heats rocks and water, with temperatures exceeding 200 degrees Celsius.
• Technology extracts energy, pumping hot water/steam from underground reservoirs.
• Steam turns turbines to generate electricity, condensed water is recycled back underground for reuse.
• Decreases need for fossil fuels, reduces greenhouse gas emissions.

Natural Gas in Ireland

• Corrib gas field discovered in 1996.
• Natural gas accounts for over 35% of Irelands energy usage.
• €3 billion boost in exports
• 800 jobs will be created.
• More then 600,000 connected to pipeline.

Explore folding in physical geography, including its causes, parts like anticlines and synclines, and the forces behind it. Learn about different types of folds, such as simple, asymmetric, and overfolds, and how compression leads to these geological formations.