Metamorphic Lab 8 - PACE UNIVERSITY – DYSON COLLEGE DEPARTMENT OF CHEMISTRY AND PHYSICAL SCIENCES SCI PDF

Preview

Summary

PACE UNIVERSITY – DYSON COLLEGE
DEPARTMENT OF CHEMISTRY AND PHYSICAL SCIENCES

SCI 101: Planet Earth Lecture/ Laboratory Fall, 2020
CRN 2020-70155 August 24 to December 5, 2020
Lecture and Laboratory Sessions: online
Instructor: Dr. Margaret Brewer-LaPorta, Adjunc...

Description

Name: Lani Komatsu

Date:

10/20/20

LAB:_8__: Metamorphic Rock Identification Introduction: The word metamorphic comes from the Greek words meaning to change form. These rocks start out as igneous or sedimentary rocks and are changed or rearranged by a combination of heat and pressure. Simply put, metamorphism occurs when a previously existing rock, known as a parent rock, is buried in the Earth under layers of other rock. The deeper the rock is buried the hotter it gets, and the higher the pressure becomes. Eventually, the rock must adjust to the new conditions of this new environment. Think of these rocks as being baked, squeezed or both in the process of becoming a metamorphic rock. Objective: You will investigate the various ways by which a metamorphic rock can be identified. Vocabulary: Please define the following terms. Foliation: any planar arrangement of mineral grains or structural features within a rock

Banded: a pattern observed in metamorphic foliated rocks from exposure to heat and directed pressure; the pattern consists of alternating layers of at least two different mineral compositions

Parent Rock: the rock from which a metamorphic rock formed

Procedure: 1. Open the PowerPoint showing the metamorphic rocks. 2. Write down the rock sample numbers on the metamorphic rock chart. 3. Determine the texture and composition of each rock sample. Use the flow chart below to help you. a. Texture: is the rock foliated or not? Write down your answer in the rock chart next to the sample number you are examining. i. Foliated: see parallel lines or bands in the rock. ii. Non-Foliated: do not see parallel lines or bands, see crystals instead. b. Composition: This you cannot “see” in a slide, so I will guide you. Write down your answer in the rock chart for the sample number you are looking at. i. Quartz: this mineral is hard, it scratches glass and has a Moh’s Hardness of 7. ii. Calcite/Dolomite: this mineral is soft, has a hardness of 3 to 4. Both minerals fizz in a weak acid. iii. Carbon: black in color. iv. Various minerals: nothing you can do about that in a slide. I will tell you on the slide if you have various minerals.

4. Complete the rest of the report sheet using your samples and the chart from the Reference Tables titled “Scheme for Metamorphic Rock Identification”.

Discussion Questions: (Answer in complete sentences) 1. Why do you seldom see fossils in metamorphic rocks? You seldom see fossils in metamorphic rocks due to the nature in which metamorphic rocks are formed. Metamorphic rocks are formed from regional or contact metamorphism. Being exposed to the high heat and concentrated pressure necessary to form a metamorphic rock, the fossil is usually either destroyed or distorted.

2. Why is a quartzite very hard and denser than its parent rock? Quartzite is very hard and denser than its parent rock because it undergoes the metamorphic process. Through exposure to intense heat and pressure, the grains in quartz compact and become tightly interwound with each other.

3. How can you differentiate between white marble and white quartzite? You can differentiate between white marble and white quartzite because of their differing compositions. By pouring acid on both one will fizz, and one will not. The marble will fizz (when powdered or crushed) due to its limestone parent rock, while the quartzite will not since its parent rock is quartz sandstone (which does not react with acid).

4. Why do metamorphic rocks often rearrange in layers? Metamorphic rocks often rearrange in layers due to the immense pressure and heat being exerted on the parent rock. The minerals will align or exchange under these conditions in order to stabilize itself during this intense process. The once random orientation of minerals is shuffled into stable bands/bonds perpendicular to the orientation of the force.

5. Why are metamorphic rocks formed by contact metamorphism usually not as dense as those formed by regional metamorphism? Metamorphic rocks formed by contact metamorphism are usually not as dense as those formed by regional metamorphism because contact implies the rock was altered by high temperature without extreme pressure. Contact rocks are often found on the boundary between pre-existing cooler rocks and are “baked” at a high temperature. Under extreme pressure (like that seen in regional metamorphism), minerals will compact making rocks formed by regional metamorphism denser....