Earth

Earth

radius3957 miles

Earth: Then and Now•(4.6 Billion years ago)

Differentiation: Process that led to Earth’s layers; Denser materials like Iron sank to the center, and lighter materials rose to the crust

Earth’s Interior3 Compositional Zones

Crust-thin, outermost layer- varies in thickness-continental crust is thicker than oceanic crust

Mantle- middle layer- more dense than the crust

Core- central sphere- iron and nickel

Earth’s Interior

5 Structural Zones

Lithosphere- crust and upper mantle- rigid layer

Asthenosphere- less rigid layer of the mantle beneath the lithosphere- ‘plastic’ means that it flows very slowly

Mesosphere- Lowest part of the mantle- solid rock

Outer Core- liquid

Inner Core- solid

How do we know anything about the interior of Earth?

Kola Superdeep Borehole(1970-1989)

12,261m180° C

How deep can we drill into Earth?

CAT Scan

Using Seismology:

Earthquakes generate waves that travel through Earth and are recorded on the surface.

Exploring Deep EarthSeismology, Gravity, Geomagnetism

Seismometer

(real life)

Continental Drift:

The hypothesis that states that the continents once formed a single landmass, broke up, and drifted to their present locations

Scientist: Alfred Wegener1912

15 major plates (and many smaller ones)

Pangea

Supercontinent that formed 300 million years ago and that began to break up beginning 250 million years ago

Evidence for Continental Drift• 1. Fossil Evidence

– Found small extinct land reptile fossils on both South America and Africa continent which had lived 270 million years ago.

• 2. Rock Formations– The ages and types of rocks in the coastal

regions of widely separated areas matched closely.

Identical fossils match up on different continents

Rocks and mountain formations match where continents used to meet

Evidence for Continental Drift• 3. Climatic Evidence

– Geologists have found glacier debris in Africa and South America suggesting they were once in a colder region. Plant fossils from the tropics at the poles.

• 4. Shape of the Continents– The Shape of the continents fit together like a puzzle

such as South America and Africa.

Several continents show evidence of having glaciers in the past

1858 Map – Continents fit together

Plate Tectonics

Plate tectonics is the theory that explains how large pieces of the lithosphere, called

plates, move and change shape.

How do they move around the planet?

Convection

Convection is the movement of heated material due to differences in density that are caused by differences in temperatures

Convection in everyday life

link

Evidence for plate tectonics

Locations of earthquakes

Locations of volcanoes

Mid-Ocean Ridges (MOR)

Oceanic crust was formed more recently than almost all continental crust, and the youngest of all crust is at

the MORs.

Seafloor spreading:

New oceanic lithosphere forms as magma rises to Earth’s surface and solidifies at a mid-ocean ridge

Magnetic reversals and magnetic symmetry:

Earth’s magnetic field has flipped direction in the past, meaning that sometimes magnetic

North is towards Earth’s North Pole and sometimes magnetic North is towards Earth’s

South Pole.

Newly formed ocean crust gets magnetized

Makes ‘Stripes’ of Normal and Reverse Polarity

‘Stripes’ symmetrical around mid-ocean ridge

North Geographic Pole: the point in the northern hemisphere where the Earth’s spin axis meets the Earth’s surface

North Geomagnetic Pole: the point in the northern hemisphere today where the pole of an imaginary bar magnet producing Earth’s field meets Earth’s surface

North Geographic Pole: top of Earth

North Geomagnetic Pole: where your compass points

Rocks with iron in them got magnetized by Earth’s field!

Paleomagnetism: studying magnetization of old rocks

Earth’s field sometimes flips (Reverses)

Types of plate boundaries

Divergent Boundaries

• Divergent boundaries occur when plate are rifted, or split, apart and begin to move apart.

• Creates large sections of oceanic crust. • Crust is created in this type of boundaries.

Off the coast of Central America

Convergent Boundaries

• Convergent means to converge, or bring together.

• Plate boundaries in which one plate (Oceanic) is pushed down under another (Continental) plate.

• Oceanic crust is destroyed at this type of boundary.

Off the coast of Chile

Oblique-Slip Boundaries

• Boundaries in which one plate slide past another with neither loss or creation of crust.

• San Andreas Fault• Also called “transform boundaries”

San Andreas Fault, California