Rocks and the Fossil Record In 1788 a

Rocks and the Fossil Record  In 1788 a

Rocks and the Fossil Record In 1788 a man named James Hutton wrote Theory of the Earth. In it he hypothesized that all the processes that we observe today, such as erosion and

deposition, remain uniform. That is, they dont change over time. They happen repeatedly in the same way. We call this theory uniformitarianism. Basically, it is the idea that the same geological processes have been shaping the Earth throughout its history.

Huttons theory caused controversy, since it meant that the Earth was much older than people had previously thought. People believed that the Earth was only a few thousand years old. That wouldnt be enough time to have allowed for the processes that Hutton proposed.

Most scientists at the time believed in another theory, called catastrophism. This theory proposes that all geologic change on the Earth happens suddenly, as in a catastrophe.

It wasnt until the geologist, Charles Lyell published his books, called Principles of Geology (1830 1833), that scientists began to believe that uniformitarianism was the guiding principal of geology.

Geologists today realize that neither theory explains all of the geological changes that have occurred during Earths long history. While we are studying the geology of the Earth we need to also look at the organisms that inhabit it and the conditions under which they

live. Paleontology is the branch of biology that studies the forms of life that existed in former geologic periods. Paleontologists are the scientists that engage in this study.

The data that they use is mainly fossils. Fossils are the remains of ancient animals and plants, the traces or impressions of living things from past geologic ages, or the traces of their activities. Fossils have been found on every continent

on Earth. The word fossil comes from the Latin word fossilis, which means "dug up." Most fossils are excavated from sedimentary rock layers . Sedimentary rock is rock that has formed

from sediment, like sand, mud, small pieces of rocks. Over long periods of time, these small pieces of debris are compressed (squeezed) as they are buried under more and more layers of sediment that piles up on top of it. Eventually, they are compressed into sedimentary rock.

The layers that are farther down in the Earth are older than the top layers. Determining whether an object or event is older or younger than other objects or events is called relative dating.

Layers of sedimentary rocks form one on top of the other, as seen in the photo on the right. The principle that states that younger rocks lie above older rocks in undisturbed sequences is called

superposition. Superposition Forces within the Earth have disturbed some rock sequences. These forces can push other rocks

into the sequence, tilt or fold rock layers, and break sequences into movable parts. They can even tilt them until they are upside down, making it difficult for geologists to determine the relative age of the rocks.

To help with this problem, geologists have combined data collected from all the known undisturbed rock sequences from different parts of the world. From this data geologists created the geologic column.

Since scientists assume that sediment is deposited horizontally to form layers, if the rock layers are not horizontal, something must have happened to disturb them. Folding and tilting are two types of events that disturb rock layers. These events are always younger than the rock layers they effect.

Faults, intrusions, and the effects of folding and tilting can make dating rock layers a challenge. Sometimes, layers of rock are missing altogether, creating a gap in the geologic record.

Missing rock layers create breaks in rock-layer sequences called unconformities. An unconformity is a surface that represents a missing part of the geologic column. Unconformities also represent missing time time that was not recorded in layers of rock. When geologists find an

unconformity, they must question whether the missing layer was never present or whether it was somehow removed. This figure shows nondeposition.

Recently Viewed Presentations

  • Undergraduate Academic Reviews - Brock University

    Undergraduate Academic Reviews - Brock University

    Workday is now automatically sending this information to the Union when the applicant accepts an offer. Article 15.01(b): Course Evaluations Evaluations are to be completed by the supervising instructor at the end of each contract
  • Building Buy In Amanda Norton, MSW Improvement Advisor

    Building Buy In Amanda Norton, MSW Improvement Advisor

    "The part of the diffusion curve from about 10 percent to 20 percent adoption is the heart of the diffusion process. After that point, it is often impossible to stop the further diffusion of a new idea, even if one...
  • More Large-Scale Machine Learning Perceptrons Support-Vector Machines Jeffrey

    More Large-Scale Machine Learning Perceptrons Support-Vector Machines Jeffrey

    Possibly w and do not exist, since there is no guarantee that the points are linearly separable. Example: Kernel Functions Can Linearize. Sometimes, we can transform points that are not linearly separable into a space where they are linearly separable.
  • Transplant Administrators Committee (TAC) - UNOS

    Transplant Administrators Committee (TAC) - UNOS

    Transplant Administrators Committee (TAC) Spring 2018 Start planning now for the 2018 UNOS Transplant Management Forum (TMF), to be held April 24 -26 in Austin, TXat the Renaissance Austin Hotel.
  • Land Planning Concepts - University of Minnesota Duluth

    Land Planning Concepts - University of Minnesota Duluth

    Land Planning Concepts ... planning system Response to growing recognition in the U .S. that attempts to define and implement recreational carrying capacities were both excessively reductionistic and failing. Carrying capacity concept itself was based on biological models.
  • MFC Student Success Symposium Feb '11 Presentation

    MFC Student Success Symposium Feb '11 Presentation

    Agenda Supporting Student Success through an Alternative Model: The Monsignor Fraser College Experience Introduction/Welcome Msgr. Fraser College (Presentation) Video: Student Testimonials Q & A Guided Campus Tour Exit Survey Annex Isabella Yonge & Lawrence Midland North Norfinch Midland THE ANNEX...
  • Bladensburg High School - Prince George's County Public Schools

    Bladensburg High School - Prince George's County Public Schools

    Bladensburg High School Parent's Night January 14, 2015 Mathematics Department Goals of Parent Night To understand courses your student must take to meet the new graduation requirements To better understand the rigor of high school To lessen the stress and...
  • Methods of Psychological Inquiry Psychology 241

    Methods of Psychological Inquiry Psychology 241

    What makes a theory a good one? Falsifiability - testable Explanatory adequacy - explain as much data as possible Parsimony - a simple theory is preferable to a complicated one Productivity - suggests hypotheses to test with new data The...