Geography Grade 9

Composition of the Earth

  • Earth's layers (like an onion): crust, mantle, outer core, inner core.
  • Layers increase in density toward the center.

The Crust

  • Thin outer layer where we live.
  • Varies in thickness: 5km (ocean floor) to 70km (land).
  • Continental crust (land): Silica and aluminum, older, thicker (25-90km), less dense.
  • Oceanic Crust (water): Silica and magnesium, younger, thinner (5-10km), denser.

The Mantle

  • Much thicker than the crust: almost 3000km deep.
  • Tectonic plates: crust + outer mantle (lithosphere).
  • Plates move slowly (inches per year).
  • Plate boundary: where plates meet; movement causes earthquakes.

Outer Core

  • Made of iron and nickel; very hot (4400-5000+ degrees Celsius).
  • Metals are liquid.
  • Creates Earth's magnetic field, which shields from solar wind.

Inner Core

  • Also iron and nickel, but solid due to immense pressure.
  • Hottest part of Earth: over 5000 degrees Celsius (like the sun's surface).

Continental Drift

  • Alfred Wegener proposed continents were moving (1912), not accepted until 1950s due to lack of proof.
  • Evidence: matching fossils, coastlines, rock formations in South America and Africa.
  • 225 million years ago: Pangaea (super continent).
  • Mantle convection currents split Pangaea into Laurasia (north) and Gondwana (south).
  • Laurasia: North America and Eurasia.
  • Gondwana: South America, Africa, Australia, and Antarctica.
  • Continents continue to move.

Plate Boundaries

  • Plates move on the mantle, causing stress/friction at boundaries.
  • Stress/friction causes earthquakes, volcanic activity, and fold mountains (e.g., Himalayas).

Types of Plate Boundaries:

  • Constructive (Divergent): Plates move apart; magma rises, cools, forms new crust; mid-ocean ridges, volcanoes (e.g., Mid-Atlantic Ridge).
  • Destructive (Convergent): Plates move toward each other; subduction occurs (oceanic under continental); ocean trenches, volcanoes, island arcs (e.g., Ring of Fire).
  • Collision (Convergent): Two continental plates collide; folded mountains form (e.g., Himalayas); earthquakes occur.
  • Conservative (Transform): Plates slide past each other; pressure builds, releases in sudden jerks causing earthquakes; faults (e.g., San Andreas Fault).

The Mediterranean Region

  • Located on Eurasian and African plate boundary (destructive).
  • Plates move towards each other causing earth movements.
  • Volcanic activity: Etna (Sicily), Vesuvius (Italy), Stromboli, Vulcano, Lipari, Pantelleria and Linosa ( next to Sicily), Santorini (Greece).

Earthquakes

  • Sudden shaking of Earth's surface, releasing stress.
  • Most last less than one minute.
  • Focus: point inside crust where pressure releases.
  • Epicenter: point above focus on Earth's surface; strongest waves/damage.
  • Energy released as seismic waves.

Tsunamis

  • Large ocean wave caused by underwater earthquake or volcanic explosion, not tidal waves.
  • Water flows straight, causing significant damage.
  • Signs: ground shaking, sudden sea level withdrawal, loud noises.

Earthquake Hazards

  • Earthquakes destroy settlements and kill people.
  • Aftershocks increase damage.
  • Anti-seismic structures (springs in foundations) help absorb tremors.

Earthquake Hazards (Examples):

  • Social: death/injury, destroyed homes, disrupted services, contaminated water.
  • Economic: Business/shops destroyed, trade disruption, high rebuilding costs.
  • Environmental: Landscape destruction, fires spreading, landslides, tsunamis.

The Richter Scale

  • Measures earthquake magnitude (power) using a seismograph.
  • Logarithmic scale (magnitude 7 is 10x stronger than magnitude 6).
  • Earthquakes exceeding 6 are ‘important’, 7 are ‘major’ and 8 are ‘serious’.

Volcanoes

  • Mountain opening to molten rock below.
  • Eruptions: gases, rock, lava; cause lateral blasts, lava flows, ash flows, mudflows, floods.
  • Formed when magma rises to the surface, erupts, and solidifies over time.

Volcano States:

  • Active: recently erupted, may erupt soon.
  • Dormant: not erupted recently, but may erupt in future.
  • Extinct: erupted thousands of years ago, no possibility of eruption.
  • Eruptions near plate edges due to plate tectonics.

Economic Sectors

  • Divided into primary, secondary, tertiary, quaternary and quinary.
  • Interdependent: primary provides raw materials, tertiary provides services, etc.

Economic Sectors:

  • primary: collects or produces natural resources(farming, fishing, quarrying).
  • secondary: makes or manufactures things(house construction, factory worker).
  • tertiary: provides a service for people(health, education, retail, transport ).
  • quaternary:provides sophisticated and advanced services(software development , research and development, informational technology).
  • quinary: services provided by the highest levels of organisation in a society( government, military, education, and healthcare).

Weathering and Erosion

  • Weathering: rock breakdown.
  • Erosion: wearing away and transporting of land.

Weathering Types

  • Freeze-thaw: Water freezes/thaws in cracks, expanding and splitting rock.
  • Onion-skin: Repeated heating/cooling causes outer layers to peel off.
  • Biological: Plants/animals break down rocks (roots widening cracks).
  • Chemical: Acid in rainwater dissolves rock (faster in warm/wet places).

Weathering in Malta

  • Caves, dolines, garigue landscapes result from chemical weathering of limestone.
    *Maqluba is a doline example and Ghar Dalam, Calypso Cave are examples of caves.
  • Water dissolves calcium carbonate in limestone through cracks.
  • Garigue landscapes: razor-shaped rocks with vegetation pockets.

Land Faulting

  • Land faulting is when pressure fractures the ricks and causes them to slip.
  • Malta fractured by fault systems from rifting episodes.
  • Great Fault: Fomm ir-Rih to Madliena; land slid down between 100 and 180 metres.
  • Maghlaq Fault: Ghar Lapsi coast; rock collapsed by more than 200 meters.
  • Rift valleys formed (e.g., Pwales).

Erosion

  • Erosion wears away the land, transportation moves the material from one place to another, and deposition builds up new landforms
  • Rivers, the sea, ice and wind are the chief types of erosion.
    *Human erosion is also important.

Population

  • Demography: statistical study of human populations.
  • Distribution: how people are spread out.
  • Density: number of people per km².
    *There are positive and negative factors that encourage people to settle in a certain area

Impacts of High Population Density

  • Competition for resources (water, land, energy).
  • Social/economic strains (infrastructure, healthcare, jobs).
  • Environmental impacts (resource extraction, pollution, fossil fuel burning).

Managed by decreasing consumption, and economic changes.
Empowering women and girls reduces family size thus reducing population rate.
REEDUCING BARRIERS TO CONTRACEPTION, QUALITY EDUCATION FOR ALL AND GLOBAL JUSTICE.

Life Expectancy and Ageing Population

  • Life expectancy = years a person is expected to live;
  • Ageing population= increase in older people.

Advantages of Ageing population:

  • Increased labourers, volunteers, experience; fewer child-related costs.

Disadvantages of Ageing population:

  • Increasing costs for governments and taxpayers, healthcare pressure, decreased workforce participation.

Migration

Migration: movement of people
Emigration: Leaving native country
Immigration: moving in a country
Internal: movement within a country
External: between countries
Voluntary: for improved quality of life and personal freedom
Forces: no personal choice but has to move due to natural disasters
Legal:foreign born in a country
Illegal:without required documentation.

Reasons of migration

*Push and pull factors