Earth 120 Exam 1

John Muir

Scottish nationalist and conservationist known as the “Father of the National Parks who formed an important partnership with Theodore Roosevelt which led to expansion of national parks, monuments, and forests

Uniformitarianism

The idea that geological processes take a very long time before forming the geologic features we see in present day.

Objective observation

Based on verifiable measurement, free from personal bias

Subjective observation

Based on opinions, beliefs, or feelings

Abraham Ortelius

Cartographer, geographer, and cosmographer from the spanish Netherlands who believed “the America were torn away from Europe and Africa by earthquakes and floods if someone considers the coasts of the three continents”

Alfred Wegener

A German meteorologist and polar researcher who proposed that the continents had all once been joined together as a supercontinent called “Pangea.”

Evidence for continental drift

Fit of the continental landmasses, fossil distributions, rocks, climate

How do fossil distributions show continental drift?

Animal and plant fossils were spread across continents that could not travel across oceans.

Name 3 animal fossils that support continental drift

Lystrosaurus (land reptile), Mesosaurus (freshwater reptile), Cynognathus (land reptile)

Mesosaurus

Marine reptile found in the Whitehill Formation of Southern Africa, as well as the Melo and Irati formations of Uruguay and Brazil

Cynognathus

Mammal-like land reptile found in South Africa and Argentina

Glossopteris

Now-extinct trees found in lowland vegetation and swampy environments. Fossils have been found in South America, Africa, India, Australia, New Zealand, and Antarctica

How do rocks provide evidence for continental drift?

Appalachian mountains are similar to the Scottish Highlands

How does climate provide evidence for continental drift?

Coal and glacier deposits that would not otherwise have formed in the climate they are in now were found in differing climates

Rejections of continental drift

Wegener had no proof of the force that caused the continents to move.

How did the depth of the ocean floor contribute to Wegener’s argument?

The discovery of mid-ocean ridges showed that something was moving in Earth.

Bathymetry

The shape of the seafloor surfaceS

Sonar

Ship emits a sound pulse that travels down through the water, bounces off the seafloor, and returns up through the water as an echo to a reciever.

Marie Tharp

The first person to discover mid-ocean ridges and produce the first complete world map of the ocean floorsM

Mid-ocean ridges

The most prominent topographic feature on the Earth’s surface

How did magnetic signatures on the ocean floor help the continental drift argument?

Ships traveling with compasses noticed that their directions would be weird due to the volcanoes erupting on ocean floors.

Magnetometry

Earth generates a magnetic field, approximated like a bar magnet and used for navigation. When volcanoes erupt on the ocean floor (which is primarily composed of the Magnetic rock basalt), the material has a random magnetization - but the dipole of an ancient rock doesn’t always align with the present.

How did the discovery of the age of the ocean floor contribute to the argument of continental drift

Younger and older parts meant that the ocean floor mass was changing too

Plate

A large rigid slab of solid rock

Tectonics

To build (Greek)

Plate Tectonics

How the earth’s surface is built from plates and how these plates move

Convergent boundaries

When plates move away at the boundary.

Subduction

When an oceanic and continental plate converge, the denser of the two plates (the oceanic one) is forced back down into the mantle, causing large earthquakes, volcanoes, and oceanic trenches

Continent - continent convergent boundary

Collision of two continental plates after any oceanic crust was fully subducted. Plates crumple together and thicken, resulting in intense deformation, fault lines, tall mountain ranges.

Divergent boundaries

Rifting-plates pulling apart at a boundary. The earth’s crust is stretched causing it to fracture as magma rises up to create new crust, resulting in creating new crust and large amounts of underwater volcanism.

Transform boundaries

Formed when two plates move laterally past one another, resulting in moderate earthquakes and linear features offsetting.

Arthur Holmes

Man who sugests that mantle convection could move the continents like a conveyor belt.

Seismology

The study of earthquakes, seismic waves, and the Earth’s interiorP

P-waves

Compression waves through solids and liquids

S-waves

shear waves that travel through only solids

Seismic topography

A technique for imaging the Earth with seismic waves produced by earthquakes or explosions

Compositional layers of the earth

Continental crust (10-70 km), Oceanic crust (5-7 km), Mantle (2900 km), core (6396 km)

Mechanical layers of the earth

Lithosphere (10-200 km), Asthenosphere (660 km), Mesosphere, Outer core (5150 km), Inner core (6396 km)

Crust

The thin outer shell of the earth

Continental crust

Relatively low density, composition similar to granite, 10-70 km thick

Oceanic crust

Relatively high density, composition similar to basalt, 7-10 km thick

Mantle

Extends from the bottom of the crust to a depth of about 2900 km, solid and rocky, accounts for ~2/3 of Earth’s mass and 84% of Earth’s volume, temps range from ~200 to 4,000 deg C, solid due to high pressure but behaves as a viscous fluid over geologic timescales

Core

The densest elements of the Earth that sunk to the middle upon Formation. Made up of mostly iron, nickel, and oxygen.

Lithosphere

The strong, upper layer of the Earth

Asthenosphere

The weak and easily deformed layer of the Earth that acts a “lubricant” for the tectonic plates to slide over

Outer core

High temps (~5,000 K) keep it liquid, generates Earth’s magnetic field through circulation of molten iron

Inner core

Center of the Earth where immense pressure forces iron and nickle into a solid crystalline structure

Geothermal gradient

The temp increaes ~25-30 deg C per km in the continental crust

Heat sources of the Earth’s layers

Primordial heart from Earth’s formation + ongoing radioactive decay

Criteria for a mineral

Naturally occurring, solid, a distinct crystalline structure, a specific chemical composition, inorganic, formed by geologic process