1 of 4 | P a g e Optional Field Trip Evidence of Global Change and Environmental Geology in South End Halifax GEOL 1208 Environmental Geology Dr. Howard Donohoe Field Trip Revised March 2016, Nov 2016 Purpose of the Field Trip At the suggestion of several students in their mid-term course review, I decided to consider an optional field trip. The idea was to provide a chance for some students in GEOL 1206 Global Change and GEOL 1208 Environmental Geology to see the world the way that geoscientists see it. Using the rocks, landforms and man-made structures in south end Halifax, this field trip will demonstrate how global change events in the geological past and the historical past have changed the nature of our south end environment. Safety and Hazards All field trips have some element of risk associated with them. On this field trip I will discuss safety issues before we begin the field trip. You may choose not to go on the field trip or not to participate in a particular stop. I am a trained first aider and I have a first aid kit. If you have any safety concerns or need first aid, talk with me. The principle hazard on this field trip is crossing city streets. Use caution, look both ways and when the street is clear of traffic, cross it. When we are in Point Pleasant Park, be careful as you walk. Listen to the Field Trip Leader about directions. Field Trip Route The starting point is the front door of McNally Main Building. We continue across campus to the Tower and then along Tower Road to the railway overpass. Credit for the Field Trip To earn the maximum credit for the voluntary field trip, you will need to do two things: 1. Complete the questions in groups of two to four and hand them in as a group and 2. Write your thoughts on what you have learned and reflect on why it is important to you. Connect the field trip, geological processes or environmental problems with your own life or draw connections with events in the media. 2 of 4 | P a g e Both are due on Friday, 31 March 2017. Tips for Earning Higher Marks  Do some reading prior to or after the field trip.  A fascinating description of the origin of Halifax Harbour with excellent illustrations and descriptions can be found at http://www.bedfordbasin.ca/halifaxharbour/origin_halifax_harbour-eng.php.  Acid rock drainage (ARD) is described at http://en.wikipedia.org/wiki/Acid_mine_drainage. This description from Wikipedia is good and is a simple explanation for a very complex chemical reaction.  Understand this chemical equation: 4FeS2 + 15O2 + 2H2O  2Fe2(SO4)3 + 2H2SO4 Iron pyrite + oxygen reacts to form hematite (red-brown colour) + sulphuric acid.  The mineral pyrite is FeS2 (ferric di-sulphide).  Sulphuric acid is represented by the formula: H2SO4.  The Halifax Formation (slate B a metamorphic rock) has large amounts of iron-pyrite in it. What happens when the pyrite is oxidized? Think acid rock drainage (ARD)!  After reading the suggested material, reflect on what you would like to learn. General Geology of the Halifax Area Four groups of rock exist in Halifax. The oldest rocks are the metamorphosed sandstones of the Goldenville Group, which are about 520 Ma. You can see these rocks on the facade of McNally Main. The next oldest are the slates of the Halifax Group shown in the bedrock behind the Sobey Building and in the dry wall next to the Continuing Education building. These slates are about 480 Ma. The granite found in the façade of the McNally Main was quarried at Purcell’s Cove and is 380 Ma. Lying on top of all rocks are debris left from the last glaciation (>10 Ka). STOP 1. McNally Main. The facade of McNally Building on Robie Street is built with grey granite (igneous) of the Halifax Pluton (a body of once molten rock called magma) and green-grey quartzite (metamorphic) of the Goldenville formation. Both of these rocks are hard and found locally. Granite quarries were located at the mouth of Northwest Arm at Purcell=s Cove. Quartzite came from quarries in Halifax or the Porter=s Lake area (east of Dartmouth). 1. Why are building stones such as granite used in buildings? (4 pts) STOP 2. Dry Wall at Continuing Education Building. The local bedrock is Halifax Formation slate B a metamorphic rock produced when shale, a finegrained sedimentary rock, has been subjected to high heat and directed pressure. The rock in the 3 of 4 | P a g e dry wall is Halifax Formation found under our feet. During its formation in the deep Iapetus Ocean at approximately 450 Ma, we geoscientists believe at that time the large-scale bottom currents did not bring any oxygen to the bottom of this ocean floor. In the absence of oxygen, pyrite was formed with the help of Sulphur-loving bacteria. Now, when the rock is exposed at the surface, the pyrite weathers chemically according to the formula on page 3. Look closely at the formula and think about the products of the reaction and their affect on the environment. Note the holes in the rock and the red-brown stain. The holes were once pyrite. The re-brown to yellow-brown stain is hematite (same mineral that colours your blood red). 2. Consider the rocks in this dry wall. What mineral has been weathered from this rock? What is the evidence? (2 pts) 3. How can the weathering of these rocks influence local ecosystems? (4 pts) STOP 5. Outcrop behind the Sobey Building. This is an outcrop of the Halifax Group slate. It is solid rock that goes deep into the earth and is thus called bedrock. 4. What has happened to this outcrop? Give a brief geological history – build a story. (4 pts) STOP 6. Tower Road Overpass. This cut was excavated in the earlier part of the century to allow access to the newly built Ocean Terminals. After the Halifax Explosion in 1917, the Richmond rail yards located next to North Street were destroyed and the Intercolonial Railroad (predecessor of CN) decided to build a whole new development in the South End of the city. 5. What rock was excavated in building the cut and the rail line? (2 pts) 6. Explain the geological hazards associated with excavations and this particular rock and rock cut. (4 pts) STOP 7. Beach in Point Pleasant Park As sea level rises, beaches change location. Look for the evidence of change. 7. What is happening to the beach now? (2 pts) 8. What can be done? (4 pts) 9. Why is the harbour where it is? (4 pts) Total points: 30 4 of 4 | P a g e

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