Geology Field Investigation Parent Training Wellesley Elementary - - PowerPoint PPT Presentation

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Geology Field Investigation Parent Training Wellesley Elementary - - PowerPoint PPT Presentation

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Geology Field Investigation Parent Training Wellesley Elementary Schools Fall 2016 1 Training Objectives To provide background information for the fourth grade geology field investigation To familiarize parent volunteers with

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Geology Field Investigation

Parent Training

Wellesley Elementary Schools

Fall 2016

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Training Objectives

  • To provide background information for the

fourth grade geology field investigation

  • To familiarize parent volunteers with

important geological sites in Wellesley

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Presentation Outline

  • Geology 101: Structure of the Earth
  • Changes to the Earth’s Surface
  • Wellesley’s geological sites
  • Geology of Wellesley video
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The Structure of the Earth

Crust: relatively cold, thin, brittle solid fractures with earthquakes made of calcium, sodium, and aluminum silicate minerals 5-20 miles (8-32km) thick thickest at mountains thinnest at ocean floor Mantle: an elastic solid most of the earth’s mass. made of iron, magnesium aluminum, silicon, and oxygen convection currents cause crustal plates to move 1832° F (1000° C) 1800 miles (2896km) thick Liquid outer core: made of iron and sulfur 6692° F (3700° C) 1400 miles (2252km) thick Solid inner core: made of iron remains solid due to immense pressure and high heat 9000° F (5000° C) 800 miles (1287km) to center

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Plate Tectonics

  • Plate tectonics is the movement of the earth’s crustal plates due to convection currents in

the mantle

  • As plates move they may collide, pull apart or rub past each other
  • The earth’s land masses sit atop these crustal plates and are deformed by crustal motion
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Stories in Stone

Every rock tells a story:

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what has happened to it since

how it formed and

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Changing Earth

  • How do mountains shrink?
  • How do boulders become small pebbles?
  • How do sharp rocks become smooth and

rounded?

  • What makes sand?

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Answer?

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Weathering

  • Weathering: “breaking down” forces – things that break

rocks & minerals into smaller particles

  • Physical
  • Chemical
  • Biological

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Physical Weathering

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wind moving water

rain, rivers, waves and storms - greatest cause of physical weathering

temperature (ice)

wind carrying pieces

  • f debris can sand-

blast surfaces freezing/melting cycles- water expands when it freezes

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Chemical Weathering

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acid rain

gases in the air (from pollution or natural causes such as volcanoes) mix with rain, snow or other precipitation

  • xidation

when oxygen reacts with iron-rich minerals - rust

1908 1969

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Biological Weathering

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lichens, bacteria, fungi

  • rganisms growing
  • n rocks produce

acids and enzymes that break down and dissolve the rock

trees and plants

tree roots can break apart huge boulders

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Photos courtesy of Irene Gruenfeld

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Erosion

  • Erosion: “carrying away” forces – things that take the

broken off pieces and move them elsewhere

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Deposition

  • Deposition: “leaving behind”–rock material is laid down

(volcanoes also leave new rock)

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Hemlock Gorge

  • cave – rock material has

been worn away

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Sedimentary rock

  • Made from sediments: bits and pieces of rock and organic

matter cemented and compacted together

  • Rocks break apart and form sediments - weathering
  • Sediments transported by wind, water, and glaciers - erosion
  • Heavier material drops out first - deposition
  • Layer upon layers, flat and parallel
  • Weight of water compresses the layers
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Hemlock Gorge

  • Around 580,000,000 years old
  • Sedimentary – Roxbury

Puddingstone

  • Large rounded rocks

embedded in sandstone

  • Embedded rocks resembled

raisins in “pudding”

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Similar rock is found in Africa!

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Is this an example of weathering, erosion or deposition?

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Hemlock Gorge Roxbury Puddingstone

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Shaping New England

Glaciers

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Glacial Formations

  • 22,000 years ago – peak of the Ice Age
  • Glaciers covered New England
  • Glaciers move – push rocks and earth aside
  • Rocks get frozen in the ice and carried long

distances

  • Receding glaciers and melting ice create

new landforms

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Abrasion and Plucking

  • Glacier came from NW passing slowly over

bedrock

– Polishing the surface – Scraping in the rock – glacial striations – Plucking the backside

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Devil’s Slide

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St Mary’s Cemetery

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Different Types of Rock

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Intrusions

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  • Magma under the surface

is pushed up into any available cracks and spaces in existing rock

  • Can vary from mountain-

range-size to vein-like fracture fillings

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Devil’s Slide

  • 600,000,000 years old
  • Oldest rocks in Wellesley
  • Formed deep below the surface
  • Diorite intrusion into surrounding

granite

  • Millions of years of weathering for
  • ur granite and diorite to become

exposed at the surface

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A Volcano? in Wellesley?

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Volcanic Breccia

  • As lava moves up through cracks

in bedrock, pieces of bedrock break off

  • Bedrock pieces show signs of

stretching from the heat

  • Some lava never reaches the

surface - cools slowly, hardening underground with pieces of bedrock embedded in it

  • Over time, the volcano has

eroded away – only plug remains

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  • St. Mary’s Cemetery
  • 580,000,000 years old
  • Igneous – volcanic breccia
  • Hardened lava that never

made it to the surface

  • More breccia is found near the school in nearby

Needham – it was a large volcano

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Are these examples of weathering, erosion

  • r deposition?

Devil’s Slide

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St Mary’s Cemetery

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Eskers

  • Ridges of gravel and sand
  • Rivers and streams flowed on, in and beneath

glaciers

  • Can be over 100 ft. high, hundreds of feet

wide, and several miles long

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Longfellow Pond – Esker Trail

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Glacial Erratic

  • Erratic: a rock that differs

from native rock in size and type

  • Carried by glacial ice, often

hundreds of miles

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Note: Fairy Rock has very large pink feldspar crystals

(this tells us it cooled very slowly below the surface)

Kelly Memorial Park

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Are these examples of weathering, erosion

  • r deposition?

Longfellow Pond Esker Trail

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Kelly Memorial Park Glacial Erratic

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Kelly Field: Kettle Hole

  • Formed by a retreating (melting) glacier
  • Blocks of ice break off, getting surrounded by sand,

gravel and rocks from the melting glacier

  • Blocks eventually melt leaving a depression

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Weathering & Erosion

  • Devil’s Slide

– trees growing into the rock

  • lichen growing on the rock
  • rocks broken off the backside

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  • St. Mary’s Cemetery
  • channel cutting across the rock
  • signs of rocks eroding at different rates
  • Hemlock Gorge
  • the cave formed by water
  • rocks falling out
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Glaciers

  • Devil’s Slide
  • smoothing on front
  • glacial striations
  • plucking on back

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  • St. Mary’s Cemetery
  • smoothing on front
  • glacial striations
  • plucking on back
  • Kelly Field
  • glacial erratic
  • kettle hole
  • Longfellow Pond
  • esker
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The Geologic Time Scale

a trip through Wellesley’s geologic history

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Final thoughts:

  • Stories in Stone: every rock tells a story of how it formed

and what has happened to it since

  • Understand what a rock, or rock formations, tell you about

the geologic history of the area (i.e. glacial activity, volcanic activity, crustal motion, water action)

  • Don’t worry about specific rock names but perhaps look for

identifying traits for each type of rock: igneous – visible crystals sedimentary – layers, fossils, rounded particles

  • Generate excitement and curiosity as you learn about

Wellesley’s history through its rocks, exploring it’s volcanic past, glacial past and present day geology