Earth’s Surface Features

Anatomy of a Continent

Continents are made up of stable interior, orogenic (mountain) belts, and coastal plain (including continental shelves)
Stable interior – _____________________________________

» No tectonic activity for a long time

» Two parts:

– Shield

– Platform

Stable Interior
Shields

Precambrian rocks at or near surface

- Form nuclei of continents (Fig. 1.16)

Canadian Shield

Stable Interior
Stable Platform

- Stable Platform - Veneer of relatively undeformed sedimentary rocks covering shield

- Stable Platform, North America

Eskridge Shale in the spillway at Lake Kahola, KS

Orogenic Belts

- __________________________- – mountain building; form by continental collision

- Folding, faulting

- Younger deformed rock nearer to margins of modern or ancient continent

Young Orogenic Belts
Canadian Rockies, South of Banff, Canada

Old Orogenic Belts

Fall Scene On the Appalachian Trail at Cedar Mountain

Ocean Basins

- Continental margin

» Transition from continent to ocean

» Includes continental shelf, slope, rise

Deep Sea Floor

- Abyssal plain

» Flattest feature on Earth

» Forms from sediment deposition that buries rough volcanic features

- Abyssal ___________________

» Rough volcanic topography

- Mid-Ocean Ridge

» Continuous mountain chain on the sea floor (2-3 km above sea floor)

» Transform faults- area between ridges where crust (and plates) show relative motion

» Fracture zones - chasms formed as a result of faulting

- Deep sea trench – elongate trough; deepest places in ocean

- Deep sea trench

» Challenger Deep, Mariana Trench (11,000 m) –deepest place in ocean – WHY?

Theory of Plate Tectonics

How do the surfaces of Earth and its Moon differ?

Continental Drift Animation

- Scotese Paleomap animation (http://www.scotese.com/)

Theory of Plate Tectonics

- Lithosphere broken into series of plates that “float” on asthenosphere and move relative to each other

- What constitutes a plate?

» All parts should be moving at same velocity (speed and direction)

- Continents carried with plates

- Ocean crust is subducted, continents are not (Why?)

Plate Tectonics

- About 20 separate plates and 8 major plates (Fig. 1.16)

» Largest plate: Pacific plate

» Plate thickness: ocean: 80-100 km, continent: 100-400 km

- Include oceans and continents; most major plates include continents (except Pacific plate)

- Plates move at average rate of about 5 cm/yr

Mosaic of Plates (Fig. 2.19)

Plate Boundaries

- Plate boundaries—where different plates meet

» Divergent--plates moving apart

» Convergent--plates moving toward each other

» Transform--plates slide past one another

- Earthquakes occur at plate boundaries – earthquake epicenters (places above point where earthquakes occur) define boundaries

Earthquake Epicenters figure

Divergent Plate Boundaries

- New crust and plate being formed (Constructive margin)

- Also called “Spreading Center”

- Process: Seafloor Spreading

- Volcanism and earthquakes

- Mid-ocean ridge (MOR) – surface expression of divergent boundary in ocean

Divergent Boundary, Red Sea

What goes up, must come down.

Models of Mantle Convection

Convergent Plate Boundary

- Convergent Plate Boundaries

» Plate and ocean crust being destroyed (Destructive margin)--process called ; zone called ____ Zone

– oldest seafloor ~200 Ma old

» Volcanism and earthquakes

- Convergent Plate Boundaries

» The importance of buoyancy

– Ocean crust and plate cools with age and distance from ridge; becomes denser; subside

– More buoyant continental crust difficult to subduct; continent-continent collisions results in mountain building

- Ocean-ocean

» Deep sea trenches--long, narrow trough (ex. Japan trench, Mariana trench) (Fig. 19.22)

» Island __________--arcuate volcanic island chain built up on ocean crust (Ex. Mariana, Tonga, Aleutian islands, Sumatra)

- Ocean-continent

» Mountain belt; continental volcanic arc (Ex: Andes Mountains; Cascade Range, USA)

Earth’s Surface Features

Anatomy of a Continent

Continents are made up of stable interior, orogenic (mountain) belts, and coastal plain (including continental shelves)

Stable interior – _____________________________________

» No tectonic activity for a long time

» Two parts:

– Shield

– Platform

Stable Interior Shields

Precambrian rocks at or near surface

- Form nuclei of continents (Fig. 1.16)

Canadian Shield

Stable Interior Stable Platform

- Stable Platform - Veneer of relatively undeformed sedimentary rocks covering shield

- Stable Platform, North America

Eskridge Shale in the spillway at Lake Kahola, KS

Orogenic Belts

- __________________________- – mountain building; form by continental collision

- Folding, faulting

- Younger deformed rock nearer to margins of modern or ancient continent

Young Orogenic Belts Canadian Rockies, South of Banff, Canada

Old Orogenic Belts

Fall Scene On the Appalachian Trail at Cedar Mountain

Ocean Basins

- Continental margin

» Transition from continent to ocean

» Includes continental shelf, slope, rise

Deep Sea Floor

- Abyssal plain

» Flattest feature on Earth

» Forms from sediment deposition that buries rough volcanic features

- Abyssal ___________________

» Rough volcanic topography

- Mid-Ocean Ridge

» Continuous mountain chain on the sea floor (2-3 km above sea floor)

» Transform faults- area between ridges where crust (and plates) show relative motion

» Fracture zones - chasms formed as a result of faulting

- Deep sea trench – elongate trough; deepest places in ocean

- Deep sea trench

» Challenger Deep, Mariana Trench (11,000 m) –deepest place in ocean – WHY?

Theory of Plate Tectonics

How do the surfaces of Earth and its Moon differ?

Continental Drift Animation

- Scotese Paleomap animation (http://www.scotese.com/)

Theory of Plate Tectonics

- Lithosphere broken into series of plates that “float” on asthenosphere and move relative to each other

- What constitutes a plate?

» All parts should be moving at same velocity (speed and direction)

- Continents carried with plates

- Ocean crust is subducted, continents are not (Why?)

Plate Tectonics

- About 20 separate plates and 8 major plates (Fig. 1.16)

» Largest plate: Pacific plate

» Plate thickness: ocean: 80-100 km, continent: 100-400 km

- Include oceans and continents; most major plates include continents (except Pacific plate)

- Plates move at average rate of about 5 cm/yr

Mosaic of Plates (Fig. 2.19)

Plate Boundaries

- Plate boundaries—where different plates meet

» Divergent--plates moving apart

» Convergent--plates moving toward each other

» Transform--plates slide past one another

- Earthquakes occur at plate boundaries – earthquake epicenters (places above point where earthquakes occur) define boundaries

Earthquake Epicenters figure

Divergent Plate Boundaries

- New crust and plate being formed (Constructive margin)

- Also called “Spreading Center”

- Process: Seafloor Spreading

- Volcanism and earthquakes

- Mid-ocean ridge (MOR) – surface expression of divergent boundary in ocean

Divergent Boundary, Red Sea

What goes up, must come down.

Models of Mantle Convection

Convergent Plate Boundary

- Convergent Plate Boundaries

» Plate and ocean crust being destroyed (Destructive margin)--process called ____________; zone called ________________ Zone

– oldest seafloor ~200 Ma old

» Volcanism and earthquakes

- Convergent Plate Boundaries

» The importance of buoyancy

Stable Interior
Shields

Stable Interior
Stable Platform

Young Orogenic Belts
Canadian Rockies, South of Banff, Canada

» Plate and ocean crust being destroyed (Destructive margin)--process called ; zone called ____ Zone