GEOLOGY – EARTH’S STORY Lesson 1

Copy this statement into your notebook. Then write a few sentences about how studying the present could reveal the story of earth’s history. “The Present is the Key to the Past” - By geologist James Hutton, late 1700’s

Catastrophism A Principle that states that all geological change occurred suddenly. Catastrophes happened- Rare, sudden, events, for e.g. Earthquakes, The Noachian flood, Tsunamis, Mudslides, Creation?

Uniformitarianism In 1795 by philosopher/scientist James Hutton Wrote that earth’s landforms were constantly and gradually changing

Hutton observed… Natural forces breaking down rock… Rivers carry rock particles downstream… Deposition of sediments, forming new layers. Eventually forming new rock… He thought new rock will eventually be uplifted – or from volcanoes – creating new landforms. The cycle will start over again. He judged from the slowness of the processes that Earth must be incredibly old!

Uniformitarianism is a Principle that states that the same geological processes shaping the earth today have been constantly, slowly, and gradually, at work, throughout earth’s history

Charles Lyell In 1830 published a book, “Principles of Geology” Was a friend of Hutton and of Charles Darwin, and was influenced by Darwin’s theory of Evolution.

The great Debate! A HAPPY MEDIUM  Most modern scientists believe both principles are at work in nature

Most geological change is gradual e.g. erosion Catastrophic events do happen e.g. earthquakes

Example: An asteroid impacting the Earth is believed to have led to dinosaur extinction Tsunami in Japan, 2012 Earthquake in Chile, 2015 More?

Activities A. Apply – Do the Making Assumptions activity. Work with your seat partner! B. 1. Why do Earth scientists need the Principle of Uniformitarianism in order to make predictions? Compare and Contrast Uniformitarianism and Catastrophism?

Relative Dating: “Which Came First?” Section 6-2

What is Relative Dating? Relative Dating uses a number of Principles or Laws Compare one rock layer to another to determine if one is older or younger Does NOT give specific age of rock.

Laws/Principles used are: The Law of Uniformitarianism The Law of Catastrophism The Law of Superposition The Law Inclusions The Law of Cross-Cutting Principle of Original Horizontality Unconformities, and Disturbances,

The Principle of Superposition top younger rocks bottom older

The Geological Column What is it? What is it used for? Dating rocks – by make comparisons Identifying layers in puzzling or disturbed rock sequences

Younger rocks lie above older rocks in undisturbed sequences “Younger over older”

Disturbances caused by forces within the earth Intrusion - Fault - Tilting - Folding -

Law of Intrusion or Cross-Cutting Anything cutting across a rock layer is younger. The rock had to be there first! Cross cuts can be Igneous Intrusions, or Igneous Extrusions, or Faulting (earthquakes)

Intrusion – cross-cutting Is the dike the youngest or oldest?

A diabase dike crosscutting horizontal limestone beds in Arizona

Faults Go To: http://www.uwgb.edu/dutchs/earthsc202notes/quakes.htm

Tilting

Folding

Fault across Fold

Law of Inclusions Pieces of rock found in other layers are always older

Inclusions Which came first, the ant or the amber?

If a rock (Rock B) contained fragments of another rock body (Rock A), B must be younger than the fragments of rock A it contained. The intruding rock (Rock A) must have been there first to provide the fragments.

 Activities  P138 Activity with text chapters on note-cards. Construct the Geological Column using cutouts.

Unconformities Gaps in the record Is a surface that represents a missing part of the geological column – show missing time. Gaps caused by erosion

Types: Nonconformities Disconformities Angular Unconformities

Nonconformity Grand Canyon overlying sedimentary rocks Missing eroded layers igneous/metamorphic rocks below the nonconformity

At Corrie, England, the red rocks are early Permian, and they lie unconformably, and at a slight angle, on greyer rocks of Carboniferous age.

Angular Unconformity

Disconformity

Disconformity - A disconformity is an unconformity between parallel layers of sedimentary rocks which represents a period of erosion or non-deposition. A Nonconformity - exists between sedimentary rocks and other rocks when the sedimentary rock lies above and was deposited on the pre-existing and eroded metamorphic or igneous rock.

Nonconformities continued An angular unconformity is an unconformity where horizontally parallel strata of sedimentary rock are deposited on tilted and eroded layers

Hmwk  Complete Text Qus. Worksheet Prepare for Quiz

View Discovery Education Video: “Rocks of Ages”