2.9

• James Hutton


  He is behind the concept that the Earth is billions of years old
• James Hutton


  • He concluded that there are forces that changes the landscape of the Earth in the past
  • This conclusion is based on his observation in the geological processes that were taking place in his farm
• Principle of Uniformitarianism


  States that the current geologic processes, such as volcanism, erosion, and weathering are the same processes that were at work in the past
• Principle of Uniformitarianism


  • This idea was refined by other geologists that although the process of the past and the present are the same, the rates of this process may vary over time
• Stratified rocks


  Also known as derivatives rock, maybe fragmental or crystalline
• Stratified rocks


  • These rocks are products of sedimentary processes
  • The formation on rock layers depend on its stratigraphy and stratification
• Stratigraphy


  • It is the study of the rock layers(strata)
  • It is the branch of geology that deals with the description, correlation, and interpretation of stratified sediments and stratified rocks on and within the Earth
• Stratification


  Bedding is the process in which sedimentary rocks are arranged in layers
• Nicholas Steno


  • Danish scientist
  • Studied the relative position of sedimentary rocks
  • Sedimentary rocks are formed particle by particle, bed by bed, and the layers are piled one on top of the other
• Stratigraphic Laws


  Basic principles that all geologists use in decoding or deciphering the spatial and temporal relationships of rock layers
• Law of Superposition


  • The largest and heaviest rock layer that settled first at the bottom is the oldest rock layer
  • The lightest and smallest that settled last is the youngest rock layer
• Law of Inclusions


  • A rock mass that contains pieces of rocks called inclusions are younger than the other rock masses
• Law of Cross Cutting Relationship


  • A fault or dike- a slab rock cuts through another rock
  • When magma intrudes to the rock, that fault or magma is younger than the rock
• Law of Original Horizontality


  • Sediments are deposited in flat layers, if the rock maintains in horizontal layers, it means it is not yet disturbed and still has its original horizontality
• Law of Faunal Succession


  • First recognized by William Smith
  • Different particular strata contain assemblage of fossils by which rocks may be identified and correlated over long distances
• Law of Unconformities


  • Rock layers that are formed without interruptions are conformable
  • Describes a layer of rock that have been deformed or eroded before another layer is deposited, resulting in rock layer mismatching
• 3 Types of Unconformities


  • Angular unconformity: It originates from horizontally parallel strata of sedimentary rock that are deposited on tilted and eroded layers. It produced an angular discordance with underlying horizontal layers
  • Disconformity: It originates from horizontal sedimentary rock layers that is lifted and the top layers eroded. New sediments are deposited when they are submerged beneath a freshwater or saltwater
  • Non-conformity: It originates between sedimentary rocks, metamorphic or igneous rock when sedimentary rock lies above and was deposited on the pre-existing and eroded metamorphic or igneous rock
• Correlation


  • Process of showing that rocks or geologic events occurring at different locations are of the same age
  • A system for correlating rocks by looking for similarities in composition and rock layer sequences at different locations
• How do geologists correlate rock layers?


  • Rock types and its characteristics (color, texture, hardness, composition or its mineral content)
  • Index fossil (guide fossils or indicator fossils)
  • Bed Rock (a deposit of solid rock that is typically buried beneath soil and other broken or unconsolidated material)
• Types of correlation


  • Physical Correlation: Is accomplished by using number of criteria such as color, texture, and types of minerals contained within a stratum which make it possible for geologists to classify a particular stratum specifically
  • Fossil Correlation: Is a principle that geologists use to determine the age of rock. It uses fossil with unique characteristics, such as geologically short lifespan and easily identifiable features and use this information to estimate the age of a rock layer in other areas that contain the same type of fossil or group of fossils