SmartStarter

• What are the layers of the earth?

• Does your description depend on the chemical or physical (or both) make up?

Geological Oceanography

• Universe/Solar System/Earth Formation– Layers• 2 ways: Physical & Chemical

• Continental Drift• Seafloor Spreading– Geologic Features• Depth data – History

• Unifying Theory: Plate Tectonics

• Formation of the Universe:

• Nebular Hypothesis– Proto-Star & Proto-

Planets

Chemical: 3 layers

1800 miles

1491 miles

1411 miles

Fe

Earth's Heat

If it is cooling, where does the heat come from?

Why is it molten?

Continental Drift

• 9/16&17/2015SMARTStarter

• What is the difference between igneous rock and metamorphic rock?

• Bonus… How hot do you think the inner core is?

Igneous Rock• Cooled magma– Magma vs. lava…?

• Primary formation is recycling machine

Igneous Rock

Processes:

• Weathering• Erosion• Chemical breakdown– Leaching

• Sediment– movement

Sedimentary Rock

LAYERS• Fossils• Petroleum• Coal= fossil fuels

Metamorphic Rock

• Heat and Pressure – chemical change

What is the difference between the crust and the lithosphere?

Lithosphere vs. Crust– Crust plus upper mantle

• Why is the crust different?– Dynamic changes– Different rocks…three types– Pressure/heat make the chemical/physical

characteristics different

Rock Cycle describes why and how“rock” is different

The Rock Cycle

Law of Conservation of Mass

SmartStart 9/18 - Friday

• What processes change rocks from:– 1. magma/lava to igneous rock– 2. Igneous to sedimentary– 3. Sedimentary to metamorphic– 4. Metamorphic to Igneous

Announcements

• Return tests– Retake – requirement & responsibility

• Good things

MONDAY

• SmartStarter….

What is the name of the ocean that surrounded pangaea?

Bonus: What is the name of the person who proposed the theory of continental drift?

Continental Drift Watch this…

According to Wegener’s hypothesis, the continents move slowly across Earth’s surface in a process called continental drift.

Continental Drift

Shapes of the continents, mapmakers noticed how well the shapes of North and South America fit together with Europe and Africa.

fossils of species of land-based plants and animals were discovered on continents separated by large oceans.

Continental Drift: “Show me the DATA!”

Glossopteris

1912: Alfred Wegener proposed a hypothesis of continental drift to explain these puzzling observations. Wegener called the ancient supercontinent Pangaea.

Continental Drift

Remember what else happened in 1912?

The continents move slowly across Earth's surface over time.

Continental Drift

Panthalassa

Wegener was unable to explain how the continents could plow through the solid rock of the sea floor or what force could move entire continents.

As a result, most geologists rejected continental drift.

Continental Drift – The Missing pieces

Several decades after Wegener proposed his hypothesis, new evidence led geologists to reconsider his ideas.

New evidence helped scientists propose the theory of plate tectonics.

Sea-floor Spreading

The Mid-Ocean RidgeWhen scientists mapped the ocean floor, they found a chain of underwater mountains which they called the mid-ocean ridge.

It forms the world’s longest mountain chain.

Sea-floor Spreading: Bathymetric Data

Sea-floor Spreading

Sea-floor spreading: process by which new oceanic crust is created at mid-ocean ridges as older crust moves away.

As sea-floor spreading occurs, old oceanic plates sink into the mantle in the process of subduction.

Sea-floor Spreading

Formation of Oceanic CrustSea-floor spreading is the process by which new oceanic crust is created at mid-ocean ridges as older crust moves away.

• The mid-ocean ridge is a huge crack where magma pushes upward.

• The parts of the ocean floor on both sides of the central valley are moving apart.

• Magma from the mantle wells up and solidifies to form new oceanic crust.

Sea-floor Spreading

During sea-floor spreading, oceanic crust forms at the mid-ocean ridge. This crust gradually moves toward a subduction zone, where old crust sinks beneath a trench.

Sea-floor Spreading

Oceanic lithosphere

Oceanic crust

Mid-ocean ridgeTrench Volcano

Continental crust

Continental lithosphere

AsthenosphereSediment

AsthenosphereMagma

Subduction of Oceanic PlatesAs sea-floor spreading occurs, old oceanic plates sink into the mantle in the process of subduction. Subduction zones are near the edges of oceanic plates. As a plate sinks through a subduction zone, it bends, forming a depression in the ocean floor called a trench.

Sea-floor Spreading

Subduction occurs because, as an oceanic plate moves away from the mid-ocean ridge, it gradually cools and becomes more dense. During subduction, the force of gravity slowly pulls the dense edges of oceanic plates into the mantle, destroying old ocean floor. Sea-floor spreading and subduction together act like a giant conveyor belt.

Sea-floor Spreading

Evidence for Sea-floor SpreadingScientists discovered patterns of parallel magnetic “stripes” that were identical on the two sides of the mid-ocean ridge.

• Earth’s magnetic field has reversed itself many times. • The magnetic field causes rock crystals to line up in a

certain way before the rock solidifies. • Stripes show that new ocean floor was added to both

sides of the mid-ocean ridge.

Sea-floor Spreading

The pattern of magnetic stripes in the rock of the ocean floor is the same on both sides of the mid-ocean ridge.

Sea-floor Spreading

Normal polarity Reversedpolarity Mid-ocean ridge

Oceanic crust

Magma

Mantle

Geologists used radioactive dating to determine the ages of rock samples from the ocean floor. They found that rocks nearer the mid-ocean ridge were younger, and rocks farther from the ridge were older.

Sea-floor Spreading

Paleomagnetism

• Directions of magnetism…changes• Result…magnetic stripping of the sea floor

Oceanic vs. Continental Plates

…Basalt vs. Granite

Basalt• Basalt is predominantly composed of crystals

of grayish plagioclase feldspar, blackish pyroxene, and greenish olivine minerals and largely forms from magma extruded along divergent plate boundaries.

Granite

• Granite is predominantly composed of whitish to pinkish plagioclase and potassium feldspars and clear to whitish quartz minerals (along with minor amounts of biotite, muscovite, and horneblende minerals

Density Differences…

• Basalt. (Ocean crust) Density 2.9.

• Granite. (Continental crust) Density 2.7-2.8.

Isostatic Equilibrium

• Archimedes' principle indicates that the upward buoyant force that is exerted on a body immersed in a fluid, whether fully or partially submerged, is equal to the weight of the fluid that the body displaces… buoyancy

Isostasy

• Isostatic adjustment -

• Isostatic Rebound – glaciers tie into the story too!

The summit of Mount Everest is the highest point on Earth – 8848 m – 29,029’

Challenger Deep is the lowest point in the ocean at -10,916 m or 35,994’

1. What do you think the average height (above sea-level) of continents is?

2. Average depth of the ocean?

SmartStarter

• On average the continents are 840 m above sea level while the average depth of the ocean basins is 3730 m.

• If the earth were a smooth sphere with the land planed off to fill the ocean basins the earth would be uniformly covered by water to a depth of 2430 m.

The Red Sea between Africa and the Arabian peninsula in Asia marks a region where two pieces of the lithosphere are slowly moving apart. Over the next 100 million years, the Red Sea could become an ocean.

Africa

Red Sea

What are plate tectonics and continental drift?

Continental Drift

The theory of plate tectonics explains the formation and movement of Earth’s plates.

Wegener hypothesized that the continents were once joined in a single supercontinent, which then broke into pieces that moved apart.

Plate tectonics is the theory that pieces of Earth’s lithosphere, called plates, move about slowly on top of the asthenosphere.

According to Wegener’s hypothesis, the continents move slowly across Earth’s surface in a process called continental drift.

Continental Drift

When the early explorers began to discover the shapes of the continents, mapmakers noticed how well the shapes of North and South America fit together with Europe and Africa.Later on, geologists discovered fossils of species of land-based plants and animals on continents separated by large oceans.

Continental Drift

Fossils of Glossopteris and other plants and animals on widely separated land masses led Alfred Wegener to hypothesize that the continents had once been joined.

Continental Drift

In 1912, Alfred Wegener proposed a hypothesis of continental drift to explain these puzzling observations. Wegener called the ancient supercontinent Pangaea.

Continental Drift

Panthalassa.

Continental drift explains why the continents seem to fit together. It also explains why the fossils from a single region appear across the globe.Wegener was unable to explain how the continents could plow through the solid rock of the sea floor or what force could move entire continents. As a result, most geologists rejected continental drift.

Continental Drift

The continents move slowly across Earth's surface over time.

Continental Drift

What are the roles of sea-floor spreading and subduction in plate tectonics?

Sea-floor Spreading

Sea-floor spreading creates new oceanic crust at mid-ocean ridges. Subduction destroys old oceanic crust at subduction zones.

Where is the newest oceanic lithosphere? Oldest?

Sea-floor spreading is the process by which new oceanic crust is created at mid-ocean ridges as older crust moves away. As sea-floor spreading occurs, old oceanic plates sink into the mantle in the process of subduction.

Sea-floor Spreading

Several decades after Wegener proposed his hypothesis, new evidence led geologists to reconsider his ideas. New evidence helped scientists propose the theory of plate tectonics.

Sea-floor Spreading

The Mid-Ocean RidgeWhen scientists mapped the ocean floor, they found a chain of underwater mountains which they called the mid-ocean ridge.It forms the world’s longest mountain chain.

Sea-floor Spreading

This false-color satellite image shows a segment of the mid-ocean ridge in the Atlantic Ocean. The ridge system winds through all of Earth’s oceans.

Sea-floor Spreading

Formation of Oceanic CrustSea-floor spreading is the process by which new oceanic crust is created at mid-ocean ridges as older crust moves away.

• The mid-ocean ridge is a huge crack where magma pushes upward.

• The parts of the ocean floor on both sides of the central valley are moving apart.

• Magma from the mantle wells up and solidifies to form new oceanic crust.

Sea-floor Spreading

During sea-floor spreading, oceanic crust forms at the mid-ocean ridge. This crust gradually moves toward a subduction zone, where old crust sinks beneath a trench.

Sea-floor Spreading

Oceanic lithosphere

Oceanic crust

Mid-ocean ridgeTrench Volcano

Continental crust

Continental lithosphere

AsthenosphereSediment

AsthenosphereMagma

Subduction of Oceanic PlatesAs sea-floor spreading occurs, old oceanic plates sink into the mantle in the process of subduction. Subduction zones are near the edges of oceanic plates. As a plate sinks through a subduction zone, it bends, forming a depression in the ocean floor called a trench.

Sea-floor Spreading

Subduction occurs because, as an oceanic plate moves away from the mid-ocean ridge, it gradually cools and becomes more dense. During subduction, the force of gravity slowly pulls the dense edges of oceanic plates into the mantle, destroying old ocean floor. Sea-floor spreading and subduction together act like a giant conveyor belt.

Sea-floor Spreading

Evidence for Sea-floor SpreadingScientists discovered patterns of parallel magnetic “stripes” that were identical on the two sides of the mid-ocean ridge.

• Earth’s magnetic field has reversed itself many times. • The magnetic field causes rock crystals to line up in a

certain way before the rock solidifies. • Stripes show that new ocean floor was added to both

sides of the mid-ocean ridge.

Sea-floor Spreading

The pattern of magnetic stripes in the rock of the ocean floor is the same on both sides of the mid-ocean ridge.

Sea-floor Spreading

Normal polarity Reversedpolarity Mid-ocean ridge

Oceanic crust

Magma

Mantle

Geologists used radioactive dating to determine the ages of rock samples from the ocean floor. They found that rocks nearer the mid-ocean ridge were younger, and rocks farther from the ridge were older.

Sea-floor Spreading

Why do tectonic plates move?

The Theory of Plate Tectonics

Plate motions are the visible part of the process of mantle convection.

Convection currents form in the mantle as hot rock rises, cools and spreads out, and then sinks back into the mantle at subduction zones. These sinking slabs of dense lithosphere and heat from within Earth drive the circulation of convection currents in the mantle.

The Theory of Plate Tectonics

Heat flows from Earth’s hot interior toward the cooler surface mainly through large convection currents in the mantle. Plates are the uppermost part of a global convection system.

The Theory of Plate TectonicsLithosphere

Convection currents

Outercore

Innercore

Mantle

The heat that drives convection in the mantle comes from two sources.

• Earth was very hot when it first formed, and some of the heat moving upward in convection currents is due to the gradual cooling of its interior.

• A second source of heat is the result of the decay of radioactive isotopes that are distributed throughout the mantle and crust.

The Theory of Plate Tectonics

What are the types of plate boundaries and what are their characteristics?

Plate Boundaries

There are three types of plate boundaries: divergent boundaries, convergent boundaries, and transform boundaries.

There are about a dozen major tectonic plates.Most major plates contain both continental and oceanic crust. The edges of plates meet at plate boundaries.As the plates move apart, collide, or slide past each other, they cause changes in Earth’s surface.

Plate Boundaries

The lithosphere is broken into about a dozen large plates, which move slowly over Earth’s surface.

Plate Boundaries

The plates move very slowly, about 0.1 to 10 centimeters per year.

• Plates move away from each other along a divergent boundary. The mid-ocean ridge forms a divergent boundary. Divergent boundaries can also be found on land, for instance, in Africa.

• When plates move apart, magma rises to fill the gap and form new rock at the edge of each plate.

Plate Boundaries

• Plates come together, or collide, at a convergent boundary. The most common convergent boundary is one where an oceanic plate is subducted beneath a trench.

• At a transform boundary, plates slide past each other, moving in opposite directions. Rock is neither created nor destroyed at a transform boundary.

Plate Boundaries

Plates meet at three types of boundaries: divergent boundaries, convergent boundaries, and transform boundaries.

Plate Boundaries

Divergent Boundary Convergent Boundary Transform Boundary

Lithosphere Asthenosphere Lithosphere

Check this out…

Where do most mountains form?

Mountain Building

Geologists found that most mountains form along plate boundaries.

Some mountains form when two plates with continental crust at their edges collide along a convergent boundary.

• Neither plate is subducted during such collisions. • The crust buckles, folds, and thickens, pushing up

tall mountains.

Mountain Building

Mountains can also form along diverging plate boundaries.

• The mid-ocean ridge system forms one long chain of mountains on the ocean floor.

• In places, the mountains of the mid-ocean ridge rise above sea level. One example is the island of Iceland in the North Atlantic Ocean.

Mountain Building

The Andes, which extend along the western side of the South American plate, have risen as a result of a collision between that plate and the Nazca Plate

Mountain Building

Assessment Questions

1. According to Wegener’s hypothesis of continental drift, what is Pangaea?

a. Africa and South America before they drifted apartb. a tectonic plate located in the Pacific Oceanc. the process by which continents moved. an ancient supercontinent formed 260 million years ago

Assessment Questions

1. According to Wegener’s hypothesis of continental drift, what is Pangaea?

a. Africa and South America before they drifted apartb. a tectonic plate located in the Pacific Oceanc. the process by which continents moved. an ancient supercontinent formed 260 million years ago

ANS: D

Assessment Questions

2. What type of plate boundary causes mountain chains, such as the Himalayas, to form?

a. divergentb. convectionc. convergentd. transform

Assessment Questions

2. What type of plate boundary causes mountain chains, such as the Himalayas, to form?

a. divergentb. convectionc. convergentd. transform

ANS: C

Assessment Questions

3. What causes Earth’s plates to move? a. gravitational force between continentsb. magnetic forces in the lithospherec. global winds pushing continentsd. convection currents in Earth’s mantle

Assessment Questions

3. What causes Earth’s plates to move? a. gravitational force between continentsb. magnetic forces in the lithospherec. global winds pushing continentsd. convection currents in Earth’s mantle

ANS: D