Warm Up Explain the Principle of Horizontality. https://www.youtube.com/watch?v=YgE-dSx-fPc Explain the Principle of Horizontality. 2. You are a geologist studying the Grand Canyon. You are excited because you can see ~2 billion years worth earth’s history right here! Describe what you are seeing in this image. What information could this rock record tell you about earth’s history (relatively speaking). Include the following terms in your explanation: principle of horizontality, law of superposition, erosion, deposition, weathering, fossils.

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Good Day! Today is Monday 9/25/17! AGENDA -WarmUp -Law of Superposition -Independent Practice Index fossils Announcements: Quiz 8.E.2.2 Thurs 9/28 Rock Cycle Weathering, Erosion, Deposition Principle of Horizontality Law of Superposition Picture Day 10/4/17 Unit Test (Mastery Quiz) Earth’s History 8.E.2.1 & 8.E.2.2 Tuesday 10/10

Warm Up: Define the The Law of Superposition

Rock Record: sequence of rock layers in sedimentary rock

Law of Superposition Law of Superposition – in undisturbed sedimentary rock layers, older layers of rock lie under younger layers of rocks.

Law of Superposition Younger sediments are laid down on top of older sediments

How do we use the law of Superposition? It allows Scientists to find the Relative Age of a Rock or fossil. Relative Age is the age of the rock layer compared to another rock layer. This process used to find relative age is called Relative Dating. Ex: How old is the Blue layer compared to the red layer?

Relative Dating This can also apply to fossils found in the different rock layers. Relative Dating states that the fossil is the same age as the rock layer it is in.

Ex: Which is older- the trilobite or the fern?

Diagram of the Law of Superposition Draw this in your notes:

Exceptions to the law…. Sometimes rock layers get disturbed and moved, so older layers of rock might lie beside, above, or in between younger layers of rock.

Exception #1: Intrusions Magma can move up into existing rock layers, cool and harden to form igneous rock called an INTRUSION Intrusions are always YOUNGER than any layer it cuts through because it moved into existing layers.

Diagram: Plutonic rock: intrusive igneous rock that has slowly cooled and crystallized beneath the earth’s surface. Examples include: sills, batholiths, laccoliths, stocks etc.

Exception #2: Fault Fault- a break in the underground rock layers that happens because of movement on either side of the fault line.

Exception #3: Unconformity Unconformity– a gap in the rock record. Weathering and erosion wear rock away exposing older layers. If new layers are deposited, there will be a gap in the rock record

An Example of an Intrusion

Practice: Diagram 1 1. What is the oldest rock layer? How do you know?

Diagram 1 2. What is the youngest rock layer? How do you know?

Diagram 1 3. What is layer C called?

Diagram 1 4. List all rock layers in order from oldest to youngest.

Diagram 1 5. What is the name of the law that tells us this is true?

Diagram 2 1. Are fossils 2 and 4 from the same time period? How do you know?

Diagram 2 3. What is the youngest fossil in this picture?

Diagram 2 4. Is Fossil 5 older or younger than fossil 3? How do you know?

Diagram 2 5. List the fossils in order from youngest to oldest

Hot Question! If you found this fossil in your backyard, what could you infer about how your backyard looked in the past?

Hot Question The law of superposition states that in horizontal layers of sedimentary rock, each rock layer is ___________. a. Younger than the layer above it and older than the layer below it b. Neither older nor younger than other layers c. Older than the layer above it and younger than the layer below it d. Always older than any vertical layers

One last Question: order the letters from youngest to oldest.

Order: E - Youngest I D H B F A C G - Oldest

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Today is Tuesday 9/26/17! Announcements: Quiz 8.E.2.2 Thurs 9/28 Rock Cycle Weathering, Erosion, Deposition Principle of Horizontality Law of Superposition Picture Day 10/4/17 Unit Test (Mastery Quiz) Earth’s History 8.E.2.1 & 8.E.2.2 Tuesday 10/10 AGENDA -WarmUp --Independent Practice -8.E.2.1 Mini quiz Study Guide -HW Packet #2 - Due Tues 10/3/17

Warm Up You are a developer relocating to a new area with plans to build commercial retail spaces (shopping center, gas stations etc). Using what you know about earth’s history and geology, what type of questions would you ask geologists about the natural environment in the area (rocks, minerals, fossils, environmental hazards, water quality etc.)

Indepedent Practice The Law of superposition You will work with your 8 o’clock partner to complete the independent practice for the Law of Superposition.