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Geog 111 Lecture Outline: Internal Processes
Update: 10/8/05


Review: Introduction to Landform Study

  • prefaced by our overview of the atmosphere and the hydrosphere
  • 1. Earth and its Interior

    2. Composition of the Earth's Crust

    3. Additional Critical Concepts for Landform Study

    4. The Process of Studying Landforms

    Introduction: Internal Processes

    Internal processes key to building terrain and landforms

    1. Crustal Rearrangement

    McKnight 13.23: Major Landform Assemblages

    Assumption that the Earth's crust was rigid with continents and ocean basins fixed in place

    This assumption has been replaced by various interrelated theories of tectonics

    1a Plasticity

    Plasticity: what is it?

    Igneous rock in upper crust: two layers

    McKnight fig 14.1: Continental vs Oceanic Crust

    General crustal structure: characteristics

    1b. Isostasy

    Isostasy: what is it?

    Effects when mass is added to or removed from the Earth's crust


    ex) sediments

    McKnight 14.2: Isostatic Adjustment

    ex) ice/snow:

    Plasticity (horizontal movement) and isostasy (vertical movement) underpin the concept of continental drift

    1c. Continental Drift

    McKnight fig. 14.3: Pangaea: greek for "whole land"

    Alfred Wegener: proposed first comprehensive theory of continental drift in 1920s

    As with many scientific theories: initial disbelief

    1d. Plate Tectonics

    Increasing understanding of lower, simatic (oceanic crust)

    Sluggish thermal convection operates within earth: brings molten rock from deep in earth to the earth's surface; simultaneously pulls crustal rock into the depths and remelts it

    McKnight 14.5: MidOceanic Ridges

    1960s: Harry Hess: explaining ridges and trenches

    McKnight 14.6: Seafloor Spreading

    McKnight 14.6: Subduction

    Evidence: age of ocean crust vs. continental crust

    McKnight 14.7: Age of ocean floor

    McKnight 14.8: Plate Boundaries

    Lithosphere: mosaic of rigid plates (oceanic and continental crust)

    Where continental plates meet...

    1. Divergent Boundary: how defined

    2. Convergent Boundary: how defined

    3. Transform Boundary: how defined

    McKnight fig 14.14: Breakup of Pangea

    Animation) Continental Drift

    Continental drift: dynamic movement of Earth's crust over time

    Movement of Earth's crust results in many important earthly landform features:

    All these landforms are explained by their location near where plates meet

    Plate tectonics: young theory; new aspects of it being learned all the time

    But some major earth landforms can't be explained with plate tectonics...yet

    McKnight fig 14.16: Mantle Plumes or Hot Spots

    McKnight fig 14.17: Hawaii Hot Spot

    Change scale: look at more detailed (regional, local) scale of analysis

    2. Vulcanism

    Vulcanism: any phenomena connected to the origin and movement of molten rock

    Vulcanism consists of:

    2a. Volcanic Processes: Extrusive Vulcanism

    Magma propelled onto earth's surface: lava

    Quality of eruptions is driven by the content of the mineral silica in the lava

    Higher quantity of silica: lava explosive when reaches earth's surface

    Lower quantity of silica: lava non-explosive: Hawaii ooze

    McKnight fig 14.19: World Volcanoes

    About 550 active volcanoes in the world

    About 50 in the US, mostly Alaska

    Volcanic Landforms

    1. Lava Flows

    2. Volcanic Peaks

    2a. Shield Volcanoes (fig 14.23b)

    2b. Composite Volcanoes (fig 14.23d)

    2c. Lava Domes (fig 14.23c)

    2d. Cinder Cones (fig 14.23a)

    3. Calderas

    McKnight fig 14.25: Crater Lake, OR

    McKnight fig 14.27

    2b. Plutonic Processes: Intrusive Vulcanism

    Magma solidifying below Earth's surface into igneous rock

    Some gets pushed up into earth's crust before or after it cools

    McKnight Fig. 14.31: Six typical Igneous Intrusions

    1. Batholiths: subterranean igneous body of indefinite depth and enormous size

    Raisz Map

    2. Stocks: smaller version of a batholith

    3. Laccoliths: slow-flowing magma forced between horizontal layers of existing rock

    4. Dikes: vertical sheet of magma pushed up into vertical fractures in rock

    5. Sill: long, thin intrusion of magma between layers of existing rock

    6. Veins: smaller version of a dike

    Sum so far: Internal Processes: building up landforms

    1. Crustal Rearrangement: Earth's dynamic crust and the consequences

    2. Vulcanism: origin and movement of molten rock

    Next: the mangling of solid rocks in the Earth's crust

    3. Diastrophism

    Deformation of solid rock in the Earth's crust

    Rock is bent or broken due to pressure from below

    3a. Folding: solid rock gets bent

    McKnight Fig 14.34

    McKnight Fig 14.35: folding nomenclature

    McKnight Fig 14.36: anticlinal valleys and synclinal ridges

    WWW) Color Landforms Atlas of the US

    3b. Faulting

    Faulting: when rock breaks, and the rock on one or both sides of the break moves

    McKnight fig 14.40: fault along sidewalk


    McKnight fig 14.41: fault scarps

    Types of Faults

    McKnight fig 14.42: fault scarps

    Prominent Faulted Landforms

    1. Horst: land uplifted between two parallel faults

    3. Graben: reverse of a horst

    4. Rift Valleys

    Key issue: have to see how all of these internal processes

    Internal Processes: building up landforms: Sum

    1. Crustal Rearrangement: Earth's dynamic crust and the consequences

    1. plasticity: horizontal movement
    2. isostacy: vertical movement
    3. continental drift: from Pangaea
    4. plate tectonics: mechanism driving continental drift

    2. Vulcanism: origin and movement of molten rock

    1. Volcanic Processes: Extrusive Vulcanism: Surface

    2. Plutonic Processes: Intrusive Vulcanism: Sub-surface

    3. Diastrophism

    3a. Folding: solid rock gets bent

    3b. Faulting: crustal stresses also lead to rock being broken

    4. The Complexes of Crustal Configuration

    Next: Weathering and Mass Wasting: breaking down landforms created by tectonic forces

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