Unit 5: Planet Earth

Unit 5: Planet Earth

Lesson 1: Inside Earth

  • Structure of the Earth

    • Crust: Thin layer of solid rock.

    • Mantle: Divided into two parts:

    • Lower part: Molten rock.

    • Outer mantle: Cooler and solid, forming part of the solid lithosphere.

    • Outer Core: Composed primarily of iron (Fe) and nickel (Ni).

    • Inner Core: High density, solid iron (Fe) and nickel (Ni).

Understanding Earth's Interior

  • Seismic Waves:

    • Energy waves generated during earthquakes, help in understanding Earth's interior.

    • Travel at different speeds through various materials, aiding in determining internal structure.

Measurement of Seismic Waves

  • Seismographs:

    • Machines used to record seismic waves, detailing strength and speed.

  • Seismograms:

    • The recordings produced by seismographs, which reveal information about Earth's internal structure.

Types of Seismic Waves

  • Body Waves:

    • Two types:

    • P-waves (Primary waves):

    • Fast, compression waves.

    • Can travel through any material.

    • First waves recorded after an earthquake.

    • S-waves (Secondary waves):

    • Slower, shear waves causing side-to-side particle movement.

    • Can only pass through solids.

    • Travel through mantle, halting at outer core, indicating a liquid state.

    • Interpretation:

    • P-waves slow down in outer core (liquid), speed up in inner core (solid).

Lesson 2: Moving Continents

  • Formation of Mountains and Continents:

    • Initially believed to form from cooling, shrinking crust; now proven incorrect.

Continental Drift**:

  • Wegener's Theory:

    • Continents were once joined together (Pangaea) but have moved apart.

    • Evidence:

    • Shapes of continents (e.g., Africa and South America fitting together).

    • Identical fossils found in Africa and South America.

    • Similar rock types on the edges of both continents.

Conflicting Thoughts on Wegener's Ideas

  • Rejected due to:

    • Wegener not being a trained geologist.

    • His young age.

    • Visibility of continents drifting apart and difficulty in imagining movement.

Plate Tectonics

  • Development in the 1950s:

    • Evidence from mountain locations, earthquakes, and volcanoes.

    • J. Tuzo Wilson recognized patterns relating to ocean trenches and ridges.

    • The Concept: Tectonic plates float on the molten mantle.

    • Tectonic plate: Massive slab of solid rock, causing earthquakes and volcanic activity at boundaries.

Types of Plate Boundaries

  • Three types:

    • Divergent Boundary:

    • Plates move apart; new crust forms from magma.

    • Example: Mid-Atlantic Ridge, also Iceland divides along a divergent boundary.

    • Convergent Boundary:

    • Plates collide; subduction leads to oceanic trenches and mountain formation.

    • Types of convergence:

      • Oceanic-continental (e.g., Cascade Range in BC)

      • Continent-continent (e.g., Himalayas), with minimal subduction.

    • Transform Boundary:

    • Plates slide past each other creating faults (e.g., San Andreas Fault in California).

Lesson 3: Sudden Changes from Gradual Movements

  • Plate Movement:

    • Caused by convection currents in the mantle dragging tectonic plates.

    • Boundary Activities:

    • Location of geological activity is determined by type of boundary.

Lesson 4: Mountain Formation

  • Mountain Formation:

    • Solid rock can bend (fold) or break (fault) under pressure.

    • Rocky Mountains formed from oceanic plates colliding with North American plates, whereas Himalayas resulted from the convergence of two continental plates.

Types of Mountains

  • Faulted Mountains:

    • Created when rocks break under stress.

  • Folded Mountains:

    • Results from prolonged pressure, leading to complex folds (anticlines and synclines).

    • Example: Mt. Yamnuska exhibits both folding and faulting.

Lesson 5: Gradual Changes

  • Glaciers:

    • Covered most of Canada during cold periods; evidence includes drumlins and eskers left post-melting.

  • Weathering and Erosion:

    • Types include mechanical (breaking rocks), chemical (transforming materials), and biological (living organism action).

  • Mass Wasting:

    • Downward soil and rock movement due to gravity, can occur slowly or rapidly (e.g., landslides).