1st Semester Exam

Continental Drift Theory

  • Alfred Wegener proposed Continental Drift Theory in 1912.
  • According to Wegener, all of the continents were one supercontinent called Pangaea.
  • Pangaea then began to split into two big continents called Gondwanaland and Laurasia.
  • Later, Gondwanaland and Laurasia continued to split up into several smaller continents that exist today.

Continental Drift Evidence

  1. Matching of Continents (Jig-Saw Puzzle)

       1. The coastlines of South America and Africa look like they used to be connected.

  1. Rocks of the same Age

       1. Rock and mountain formation pick up on separate continents in the same pattern.    2. Ancient rock belts on the coast of Brazil match with those found in Western Africa.

  1. Fossils

       1. Mesosaurus fossils were found in South America and Africa

  1. Climate Evidence

       1. The presence of glacier deposits along the Ghana coast in Africa    2. Widespread glacial sediments in South America, Africa, Madagascar Arabia, India, Antarctica, and Australia

Regardless of all the evidence that proves that the continents were once closer together, Alfred Wegener’s Theory of Continental Drift was rejected due to not explaining HOW the continents moved.

It was not until 30 years after his death that Harry Hess, used sonar technology to examine the ocean floor which led to Hess’ theory of seafloor spreading

Seafloor Spreading

Seafloor Spreading is a geologic process in which tectonic plates split apart from each other.

This is a result of convection currents in the mantle (asthenosphere)

Convection Current is a force inside of the asthensphere that moves the lithospheric plates right above it.

==Hot material rises and cool material sinks==

Plate Tectonic Theory

Plate tectonic theory is when Earth’s outer shell is divided into several lithospheric plates that glide over the asthenosphere.

These plates have 3 different motions: convergent, divergent, and transform

Types of Plate Tectonics

Type of Plate BoundaryDefinitionLandform
Convergent (Land vs Land)2 continental plates collide or move towards each othermountains earthquakes
Convergent (Land vs Ocean)an oceanic plate move towards and subduct under a continental platevolcanoes trenches subduction zones earthquakes
Convergent (Ocean vs Ocean)2 oceanic plates collide or move towards each otherisland arcs subduction zones earthquakes
Divergentplates move away or drift away from each othermid-ocean ridges rift valleys earthquakes
Transformplates slide past or scrap each otherfaults earthquakes

Earthquakes

Sudden and violent shaking of the ground. The result of plate movement of Earth’s lithospheric crust.

Earthquake Waves

Seismograms are used to measure earthquake seismic waves

Primary Waves (P waves) - first wave, compressional, fast

Secondary Waves (S waves) - second wave, transverse, slower

Types of Rock

Rocks are made up of one or more minerals. They are found in nature show many different characteristics.

There are three types of rocks:

  • Igneous
  • Sedimentary
  • Metamorphic
Type of RockHow it is FormedExamples
IgneousMelting and cooling of rockbasalt granite diorite obsidian
Sedimentarycompaction and cementation of sedimentsconglomerate shale limestone sandstone
Metamorphicintense heat and pressuremarble gneiss slate quartzite
Igneous Rock
  1. intrusive igneous rock

       1. when rocks cool slowly below or ==inside== Earth’s surface

      \

  1. extrusive igneous rock

       1. when rocks cool quickly ==outside== on Earth’s surface

Sedimentary Rock
  1. Clastic sedimentary rock

       1. formed from ==mechanical weathering==

  1. Chemical sedimentary rock

       1. formed from ==dissolved materials== or ==precipitates==

  1. Organic sedimentary rock

       1. formed from accumulation of ==plant and animal debris== or ==decomposition==

Metamorphic Rock
  1. Foliated metamorphic rock

       1. exposure to heat and pressure which makes them appear ==layered==

  1. Non-foliated metamorphic rock

       1. these ==do not== show layers

The Rock Cycle

Rocks never remain the same and are always changing. The rock cycle is nothing but a process by which rocks of one type with certain characteristics change into rocks of another kind.

 

Rock Cycle: Transition to Igneous

Melting of rock → ==Magma== → Cooling of rock (Crystallization) → Igneous rock

Rock Cycle: Transition to Metamorphic

Exposure to intense heat and pressure. Can apply to igneous, sedimentary, or other metamorphic rock

Rock Cycle: Transition to Sedimentary

Weathering and erosion of rock → ==Sediment== → Compaction and Cementation → Sedimentary Rock