Geology Module 3
Other common rock forming minerals
- calcite - dolomite - clays - magnetite - pyrite - talc
The combination of internal order (crystalline nature) and chemistry result in a set of physical properties that help us distinguish between minerals, including such characteristics as:
- habit (how the mineral grows) - cleavage and/or fracture (how the mineral breaks) - colour (how the mineral interacts with light) - hardness (a function of the strength of the bonds in a mineral)
Vast amounts of rock and sediment were removed by glaciers from the Coast and Cascade mountains... where did they go?
- much found it's way to the Pacific Ocean - large amounts were deposited on coastal lowlands and in the Strait of Georgia
6 most common rock forming minerals
- quartz - feldspar - mica - pyroxene - amphibole - olvine
Terms to know
...
The rock cycle: The crust is constantly changing as external process break down the bedrock and mountain ranges by weathering and erosion and internal processes build new land again.
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end of flash module, start of VCOTC pg. 34-66
...
The rock cycle in summary: 1) when a rock is weather and eroded, surficial deposits are formed such as ________, _________, __________. The surficial deposits are also called _____________, and are transported and ultimately deposited on ___________. The process by which sediments are deposited on the sea floor is called _______. The sediments undergo diagenesis and a _______ rock is formed. 2) The sedimentary rock then has two alternative paths in the cycle. What are they? 3) Likewise, the metamorphic rock has two alternative paths, what are they? 4) The magma cools and solidifies to an _______ rock 5) The igneous rock has two possible routes, what are they?
1) - cobbles, gravel, sand, clay - sediments - sea floor - sedimentation - sedimentary 2) By mountain building, the rock can be lifted to the surface where it will again be subjected to weathering and erosion, or it can be transported deeper and subjected to metamorphism (transformed into a metamorphic rock) 3) Either it can be uplifted to the Earth's surface where it will be subjected to weathering and erosion, or it can be transported even deeper. In this way, the rock can begin to melt and a magma is formed. 4) Igneous rock 5) It can either be subjected to metamorphism and turn into a metamorphic rock, or it can rise to the surface as lava and turn into a volcanic rock (extrusive rock)
Identifying notes, please note, I don't expect you do memorize the details of classification but i'd like you to become familiar with...
how rocks are classified. The Flash module does a nice job of giving you a more global view whereas the BC Geological Survey Branch publication covers BC. For local rocks, refer to your textbook, GeoMap Vancouver and Vancouver Rocks.
Define contact metamorphism
The transformation of rocks in the contact zone around magma
Minerals are most commonly classified by:
chemical composition (dominant anion or anionic group)
Evidence of Ice Age glaciation can be seen in BC's montane erosional landforms including,,,
cirques arêtes nunatuks
Define an outcrop
an exposure of rocks that geologists study, can contain multiple rocks. we interpret relationships by examining the contacts between the rocks
Quadra sand is exposed on the sea cliffs in point grey (e.g. at tower beach). It is also an important _____
aquifer
Granite consists of these 3 minerals:
biotite (black mineral crystals, a type of mica) feldspar (pink and white mineral crystals) quartz (grey and white minerals)
Much of Vancouver's west side is located on a gently ridged surface with a distinct southeast grain, indicating...
glacial erosion by southeast flowing ice
Ice Age sediments mostly comprise of:
gravel, sand and silt deposited by meltwater streams till, on the other hand, is deposited directly from glacier ice, and is also present but a small part of the 'Ice Age' sediment package
Porosity determines
how much water, oil or gas a rock can accommodate (it is the volume of pores in relation to the volume of the rock)
All rocks consist of different types of:
minerals
A rock can undergo varying degrees of transformation and metamorphism depending on the ________ and ________ the rock is subjected to
pressure, temperature
Sand and clay are surficial deposits (early part of diagenesis), while _____ and ______ are solid rocks (later process of diagenesis)
sandstone and shale
The process by which sands are deposited on the sea floor
sedimentation
Not all features produced by glacial erosion are large. Bedrock can be striated and polished by glaciers. How?
stones and sand grains embedded in the ice act like sandpaper as they are dragged across the rock surface. These objects both scratch and smooth the rock. Glaciers can also pluck large blocks from highly fractures rocks as it is frozen into the bed of the glacier and slowly carried away. Repeated action of this sort may give rise to large rock ridges that are smooth at their up-ice ends but have ragged down-ice terminations
Glacial plucking has probably played an important role in creating the steep western face of __________
the Stawamus Chief near Squamish.
from the definition of a mineral, what does it mean that it is a "crystalline structure"?
the atoms are arranged in an orderly manner; this pattern results in a natural symmetry the outward expression of this order are the regular geometric shapes we call crystals The crystalline forms and the internal symmetry have their origin in the bonding relationships between the atoms and molecules that comprise the mineral.
In addition to the 5 classes (oxides, sulphides, sulphates, carbonates, silicates), one more group is important: ___________
the native elements. Though not necessarily the most common, these minerals are important commodities and can tell us quite a bit about the evolution of the earth
Module 3 focuses on...
the origin and distribution of Earth materials in the Vancouver region. The topics include minerals, earth materials and classification, distribution of earth materials in Vancouver, and Vancouver's multi-stage history
Minerals provide valuable clues as to...
the physical and chemical conditions that were present when a rock formed (by looking at minerals, therefore, we gain major insight into the conditions of formation)
Diagenesis
the process by which sedimentary rock is formed. As time passes, surficial deposits are laid down on the sea floor and bury older deposits, which become compacted. Pressure and higher temperature cause chemical processes that turn the deposits at depth into solid rock, formed sedimentary rock
The SiO4 tetrahedron is an important "building block" in the largest group of minerals, ________
the silicates
Explain the process of diagenesis that turns sand into sandstone
1) Sand consists mostly of small grains of quartz and feldspar, with small gaps in between the grains. As the sand become buried by new deposits, the pressure increases and the sand is compressed 2) When the grains of sand are compressed, parts of the minerals are released and precipitated 3) When pressure and temperature increase, new minerals can form which act like cement and "glue" the grains of sand together
1. Rocks on the bed of a mountain stream consist of sand, gravel and cobbles (cobbles have a round shape because...) 2. When this mixture of coarse and fine surficial deposits undergoes diagenesis, a rock called __________ is formed.
1) because they have been worn away by sand and water for thousands of years 2) conglomerate
1) In contact metamorphism, the rocks that are closest to the hot magma undergo the ______ transformation. Outside the contact zone, the rocks are _________ 2) The magma cools and solidifies into a coarse-grained ______ rock If the contact zone contains shale and limestone... 3) the shale may turn into ______ 4) the limestone may turn into _____
1) greatest unaltered (not transformed) 2) plutonic 3) hornfels 4) marble
Metamorphism of basalt (an extrusive rock in the earth's crust) 1) If basalt is transformed at 5-10km, it turns into __________. 2) At 10-20km the above rock is transformed to ______. 3) If the above rock goes further down to 40 km depth it is transformed to ________.
1) greenschist 2) blueschist 3) eclogite
1) Rocks in the oceanic plate will melt when they reach a certain depth, forming _____ 2) This body of melt can rise slowly through the crust and flow onto the Earth's surface as.... 3) When the lava solidifies, a new ________ rock is formed 4) These rocks are subjected to _________ by the weather
1) magma 2) lava in volcanic eruptions 3) volcanic 4) decomposition
when the clay is covered by 4-5000m thick deposits, the clay undergoes diagenesis and turns into shale (still sedimentary). Through diagenesis, surficial deposits are transformed into rocks. Metamorphism of clay 1) at 5-10km depth, shale is transformed (metamorphosed to) ______ 2) at 10-20 km, the above rock is transformed into _________ 3) At depths of more than 20 km, the above rock is transformed to ___________.
1) phyllite 2) mica schist 3) gneiss
After sand has been compressed and turned into sandstone (diagenesis) there are still some gaps or pores between the grains. 1) This allows space for: 2) The volume of the pores in relation to the volume of the rock is called ________
1) water, oil or gas 2) Porosity
Igneous rocks are formed when molten rock (magma) solidifies. 1. If magma comes all the way to the surface, _______ rocks are formed 2. Some magma solidifies on the way up in fractures or dykes, forming _________ rocks. 3. Magma that solidifies deep down forms ________ rocks.
1. Extrusive rocks (the magma (lava) "daylights" and solidifies) also called Volcanic rocks 2. Hypabyssal rocks (a type of intrusive rock) 3. Plutonic rocks
These elements make up the rocks in the earths crust: 1. ___________ (46.6%) 2. ___________ (27.2%) 3. ____________ 4. ____________ 5. ____________ 6. ____________ 7. ____________ 8. ____________
1. Oxygen (O)* 2. Silicon (Si)* 3. Aluminum (Al) 4. Iron (Fe) 5. Calcium (Ca) 6. Sodium (Na) 7. Potassium (K) 8. Magnesium (Mg)
Gabbro and basalt contain the same minerals. 1. But Gabbro is a __________. We know this because... 2. Basalt is an _______ rock. We know this because...
1. Plutonic rock. It has cooled slowly, the crystals feldspar and pyroxene have had time to grow large. 2. Extrusive rocks. The lava cooled quickly on the surface so the minerals did not have time to grow large
2 group activities:
1. Terminology Share: The first activity involves building an understanding of some of the terminology associated with the module (see next page). This discussion topic will open on Tuesday, February 3. Please respond to any questions put to you in a timely way. This must be complete by Monday, February 9, 11:55 PM as I will be sharing the results with the class. 2. Hypothetical Field Trip: using information posted from the GeoMap activity, you will develop a hypothetical field trip using locations that you select from your own locations and those of your colleagues (Opens Friday, Feb.6, completes on February 12). 3. Please note I have provided a worksheet to facilitate tracking these activities.
1. Where do the huge boulders that are scattered around Pacific Spirit Park and White Rock and other upland areas of the Lower Mainland come from? 2. Geologists call these boulders _______
1. They were carried on or within glaciers that flowed from the Coaast Mountains across the Fraser Lowland during the Ice Age. As the glaciers melted, the boulders were released from the ice and deposited where we see them today (some on dry land, others on the seafloor from melting icebergs) 2. Erratics
Readings in Module 3:
1. Web pages in Module 3 2. Web Module: Rocks (Flash Module) - http://bit.ly/1n5gpvV The Identification of Common Rocks by Eileen Van der Flier-Keller and William J. McMillan http://bit.ly/Mor9df | PDF - http://bit.ly/1aRBZEj 3. 4. Vancouver, City on the Edge: review pp. 24-33; read pp. 34-66. 5. Vancouver Geology (downloaded in Module 1), pp 9-57 http://bit.ly/1fltr5v 6. Geomap Vancouver (downloaded in Module 1). - http://bit.ly/1fz7Nfw 7. Vancouver Geological Map (from Vancouver Geology) - http://bit.ly/1eId8hz 8. Vancouver Rocks (poster) - http://bit.ly/1bgLszv PDF: http://bit.ly/MLSMhc
After the Ice Age: The last of the Ice Age glaciers retreated out of the Fraser Lowland back into the mountains about ______ years ago. Much of the land was the same as today, but the __________ and ____ of the Fraser River did not exist
12,000 Floodplain and delta
4) As soon as the rock has solidified on the surface, it is subjected to decomposition by the weather. 5) The rock becomes weathered and the mineral crystal becomes part of a stone that falls into a ______, which then transports the stone. 6) After a long period of transport, the stone is eroded such that the original mineral crystal has turned into a small _________. 7) This (above) is washed into the sea but the river and sinks to the sea floor, and along with many other pieces of this, undergoes _______.
4) - 5) river 6) grain of sand 7) diagenesis. The mineral grain that was originally crystallized (solidified) in the volcanic rock has ended up, for the moment, as a mineral grain in a sandstone.
Studies of cores of deep-sea sediments of Pleistocene age provide evidence for ____ major climactic cycles in the last 800,000 years
8
8) The sandstone, along with the oceanic plate it lies on, may be transported to depth and subjected ______ and _________ 9) In this way, the sandstone with be transformed and end up as a __________ rock. 10) But only for a while. Sooner or late, this (above) rock will be broken down, either by _____________ or be _____________
8) compression and high temperature 9) metamorphic rock 10) weathering and erosion at the Earth's surface, or by melting at depth
Define clay
A fine-grained superficial deposit that has been laid down on the bottom of a lake or in the sea. As the layers grow thicker, the lowermost clay will be compressed. Just like sand, the clay will undergo diagenesis - the clay becomes lithified into shale
Define a cirque
A half-open, steep-sided hollow on the side of a mountain. It is shaped like a half bowl and is commonly at the head of glacial valley. It is produced by glacial erosion.
Define a nunatak
A hill, mountain, or peak of rock completely surrounded by a glacier and is projecting above the surface of the glacier or snow.
Define an arête
A sharp, narrow mountain ridge or spur, which is normally present above the snowline in mountains sculpted by glaciers they are abound in the higher parts of the southern Coast and Cascade mountains, where some arrête summits stand above the surface of the ice sheet as nunataks
Define sand
A surficial deposit that consists of small grains of quartz, feldspar and other hard minerals. Formed by rocks that have been broken down by weathering and erosion over a long period of time Every single grain of sand consists of hard and resistant minerals
Glaciers flowing down Howe Sound during the Ice Age plucked slabs of granite along joints (a fracture in a rock) creating the steep rock face of the _____
Chief
Coast Plutonic Complex, Georgia Basin, Cascade Arc
Coast Plutonic Complex: - 60 to 200 km wide belt of granitic rocks stretching along the BC coast from the Fraser river 1700 km north to the Yukon Border. - One of the largest collections of plutons in the world - Masses of molten granitic rock formed deep within the crust and were slowly uplifted. Erosion at the surface removed overlaying rocks to expose the complex. - erosion and uplift of plutonic igneous rock signifies that a great deal of subduction has occurred in this region, as the oceanic lithospheric plate has been heated to at least 1000 degrees and melted to form magma which eventually cooled beneath the Earth's surface. Most of the plutonic complex dates back 150 million years ago during the second bedrock phase of the region. Georgia Basin - Large depression between the Coast Plutonic Complex and the Cascade Mountains. - formed during the uplift and erosion of the CPC 70 million years ago in the third bedrock phase of the region and continues today. - The area spans from Vancouver Island to South of Seattle, inland BC and north to Whistler. - Erosion carried sediments and plant debris off of the Coast Plutonic Complex into the shallow lake which was situated on the Georgia Basin which eventually formed into sandstone, mudstone and other types of Sedimentary rock. This also marked the beginning of the uplift of the Coast range. Cascade Arc - volcanic arc stretching from the state of Washington to the Fraser Canyon in British Columbia - Contains active volcanoes - made up of volcanic and sedimentary rock - Most of the Cascade Arc formed during the tertiary period, with major events occurring 50, 35 and 17 million years ago during the fourth bedrock phase of the region. - Most of the activity has occurred over 3 million years ago, and many of the volcanoes remain active today. The magma forms as the Juan de Fuca plate is forced below the North American plate and penetrates the Earth's surface, sometimes creating dykes that reach the surface. - Examples of dykes that reach the surface include Siwash rock in Stanley Park, and many rock formations in Queen Elizabeth Park
contact metamorphism, regional metamorphism, hydrothermal metamorphism
Contact Metamorphism- refers to low pressure situations, but a rapid rise in temperature with depth. Transformation that occurs to crustal rocks that come in contact with magma intrusions and are heated up. As the magma body is rising, the older rocks found around the intrusion undergoes metamorphism. The rocks that are closest to the magma undergo the greatest amount of transformation while those further away undergo little to no transformation. Regional Metamorphism- This type of metamorphism occurs as a result of changes in pressure and temperature in a large region of the crust. Regional metamorphism occurs for the most part in areas where mountain building is taking place. The thickening of the crust as a result of convergent forces causes an increase in temperature and pressure. This type of metamorphism also occurs in subduction zones. The rocks formed in these metamorphism generally show foliation, or layering, due to the applied stress. Regional metamorphism corresponds to to a line that travels through the middle of the diagram. A rock will start in the "diagenesis" facies and work its way with depth through Greenschist --> amphibolite and granulite. The classic foliated metamorphic rocks - phyllite, schist and gneiss are commonly formed under these conditions. Hydrothermal Metamorphism (hot-water-related metamorphism) - This type of metamorphism happens when rocks come in contact with high temperature fluids. This causes changes both in composition and mineral content. The fluid can be either magma intruding into country rock or from surface water. This type of metamorphism is an important process through which the oceanic crust gets hydrated and eventually causes the melting of continental crusts. This consequently causes the formation of magma at subduction zones. All three types of metamorphism take place in B.C. Most of these are created in or near subduction zones and can be visible in our own backyard.
20,000 years ago, the ____________ ice sheet covered much of Canada, buring the land surface to depths of up to 3 km. To the West was the much smaller _________ ice sheet, which covered nearly all of B.C. and the southern Yukon Territory
Laurentide Cordilleran
delta, progradation, topset, foreset, and bottomset beds
Delta: a flat, low lying geographic feature that forms at or near the mouth of a river due to the accumulation of deposited sediments that have been carried by the stream or river traveling into oceans, lakes, etc. The next 3 definitions all refer to the natural stratigraphic components that one could observe if you were to take a cross-section of a Delta in action... Progradation: the natural growth of a river delta in which the overall mass of sediments are able to accumulate faster than the river can erode and remove. This process is what gives a delta its reach further out into the sea overtime and is responsible for the area covered by the delta itself. Topset layers: the top (youngest) layer of sediment that can be seen in our hypothetical cross-section of a river delta. Topset can be chracterized by the horizontal sediment deposit of a coarser, more rocky material than you would see elsewhere in a Delta. This is the layer of a river delta where you could expect to find large rocks! The topset layer would be closest tot he mouth of the river. Foreset layers: layers that are able to accumulate beyond the topset beds and tend to settle in an inclined manner towards the general direction of the sediment transport and deposition. At foresets, one could expect to find the finer sediments like sand and fine gravel. Bottomset layers: as the Delta builds our further, foreset beds grade down into bottomset beds. This layer is deposited horizontally and is comprised mostly of clay so is therefore the lightest and finest.
foliation, bedding (layering), folding
Foliation: refers to the bands that occur on metamorphic rocks. When a metamorphic rock develops a parallel fabric. The fabric is chacterized by the growth of crystals in planes that are perpendicular to the force that is applied. The re-arrangement of minerals happens under extremely high pressure and temperature. Due to the compression, the minerals in the rocks align perpendicular tot he stress field. Bedding: refers to a rock structures' form by layers. Each of the layers is obvious and has similar sediments in it. Sedimentary rocks are often bedded. The direction of the bedding could help us to find out the direction of the wind that deposited the sand. It could also be used to determine whether it was a beach deposit or a wind deposit. Folding: folding generally forms when to plates collide. It creates wavelike deformation in the rocks. Folding is not limited by sediment and rock size. It can be found in microscopic scale to mountain sized folds. We use size, shape and tightness to identify folding types.
The ice-sheet phase of the last glaciation, referred to in B.C. as the _______ Glaciation, occurred between 20,000 and 12,000 years ago
Fraser
The Youngest Ice Age sediments in Vancouver are products of the most recent, or _______ glaciation. Thick bodies of sand deposited by streams flowing off advancing glaciers during the early stage of the Fraser glaciation are termed _______ sand.
Fraser glaciation Quadra Sand
Local examples of a fjord are _______ and _______
Howe Sound and Indian Arm
ice sheet, valley glacier, isostatic adjustment & glacial rebound
Ice Sheet: a mass of ice that extends 50,000 square km or more along the Earth's surface. During the Ice Age, parts of North America, Northern Europe, and Eurasia were covered by Ice Sheets. However today, the only ice sheets remaining on Earth are in Greenland and Antarctica, which contain over 99% of the Earth's freshwater ice. The sheets form in regions where snow that falls in winter does not melt during the summer months, piling over thousands of years to form massive bodies of ice. Ice sheets are relevant to our geological understanding of Vancouver because in the past, massive ice sheets extended over Vancouver, which is evident in Ice Age sediments. Valley Glacier: when glacial ice (perhaps in the form of an ice sheet flows downhill and erodes or enlarges an existing valley, it forms what is called a valley glacier. It is confined within an existing valley is flowing ice, and may join other valley glaciers creating more erosional power. Isostatic Adjustment/Glacial Rebound: When an ice sheet or any glacier forms on a landmass, it applies exceptional pressure on the landmass. The landmass' position on the mantle is partly a function of this pressure. Thus, by increasing the weight applied onto a landmass, an ice sheet causes that landmass to undergo isostatic adjustment (it sinks deeper into the mantle). When the glacier eventually recedes, either by melting or through water runoff, the pressure causes the landmass to rise in it's position upon the mantle in a process known as glacial rebound.
Rocks that have invaded another rock and solidified are called ______ rocks.
Intrusive (e.g. hypabyssal rocks)
Native elements:
Iron, Copper, Diamond (carbon), Graphite (carbon), Platinum, Gold, Silver, Arsenic
How were deltas formed from glacial retreat?
Large deposits of sand and gravel formed at the mouths of valleys where meltwater streams met the sea. Sediments (marine and deltaic) accumulated on the submerged lowlands. These sediments (before full deglaciation) when only the top of Burnaby mountain rose above the sea as an inland, include the large sand and gravel deltas on which part of North Vancouver has been built.
Glaciers in Western Canada have advanced on several occasions during the last 5000 years. None of these advances compares to the massive expansion of glaciers during Ice Age, but cooling between the 13th and 19th centuries was significant enough for scientists to have termed this the _______.
Little Ice Age *the maximum advance of glaciers during the last 10,000 years occurred only 150 to 250 years ago near the end of the Little Ice Age *In the 20th century, glaciers have retreated in response to a warming climate, perhaps because of greenhouse gases caused by fossil fuel burning
When a rock is subjected to greater pressure and higher temperature, chemical reactions occur between the minerals and the properties of the rock change, forming a ________ rock.
Metamorphic
mineral, mineraloid, rock & surficial deposit
Mineral: a naturally occurring inorganic compound/substance that has a definable chemical make-up and structure. They have a crystalline structure which describes its highly ordered structure and symmetrical patterns. Most minerals are said to be abiogenic meaning to be made by a process other than one involving living organisms. Mineraloid: different from minerals in that they can be composed of inorganic materials, and they lack the crystalline structure (does not represent crystallinity). Pearls are said to be a mineraloid because they are composed of calcium carbonate, but these molecules are held in place by organic materials. Other examples include obsidian and opal. Rock: Rocks are considered solid aggregates that are made up of a mixture of minerals and mineraloids. E.g. granite is a mixture of quartz, feldspar and biotite. Surficial deposit: deposits of modern and ice-age sediments that have been deposited on old bedrock. Unconsolidated alluvial, residual, or glacial deposits overlying bedrock. These sediments are considered to have been deposited during the Quaternary time frame occurring 1.8 million years ago.
Mineraloids
Naturally occurring earth materials that lack a crystalline structure and/or may form through organic processes. These substances are readily incorporated into sediments and consolidate into rocks.
oceanic trench, island arc, back-arc basin
Oceanic trench: Ongoing subduction process causes the oceanic crust to subduct below the continental crust Deep, long, narrow depression in the ocean floor They are the deepest topographic features of the ocean floor Important in determing earthquakes Deepest trench known is the Mariana trench Island Arc: Long chain of curved volcanoes that are usually formed in two's parrallel to each other The inner volcanoes are usually active volcanoes and the outer row are non volcanic islands Destructive earthquakes usually occur around the area Formed where two lithosphere converge Back-arc Basin: Submarine basin that form behind an island arc Found within the convergence of two tectonic plates Formed by the process of back-arc spreading, when one tectonic plate subducts under the other one Characterized by asymmetric seafloor spreading Relationship between terms These terms are all formed on the are where two tectonic plates are coverging. They are formed through the process of subduction Deep sea trenches lie parrallel to island arcs Subduction forms an oceanic trench and melts the mantle in the overlying plate, this then causes magma to rise to the surface. This causes volacnoes on the island arc to errupt. Additional magma would then create cracks in the crust creating one or more spreading centers which widen the seafloor and expand the area behind the trench. The basin expands forming the back-arc basin. Vancouver example On the west side of Vancouver, there lies two tectonic plates: Oceanic Juan de Fuca Plate and continental North American Plate. These two plates are converging every year at a rate of 4cm/year. This collision causes the denser Juan de Fuca plate to subduct under the lighter North American continental plate. A chain of active volcanoes are then formed
greenschist, blueschist & eclogite
One of the primary goals of metamorphic petrology is to interpret the pressures (P) and temperatures (T) at which a rock formed, or, in regional geology, the P-T history of a set of rocks. Contact metamorphism refers to low pressure situations, but a rapid rise in temperature with depth. Regional metamorphism corresponds to to a line that travels through the middle of the diagram. A rock will start in the "diagenesis" facies and work its way with depth through Greenschist --> amphibolite and granulite. The classic foliated metamorphic rocks - phyllite, schist and gneiss are commonly formed under these conditions. Subduction zones follow a higher pressure pathway typically - Blueschist facies corresponds to a high pressure, an overall lower temperature pathway than the other two. Greenschist: a major division of classification within metamorphic rocks. These types of rocks form under the lowest temperature and pressure conditions. They are found 8-50km below the surfaces. Usually produced by regional metamorphism. Blueschist: formed by regional metamorphism at high pressure and low temperature. Typical in areas of subduction, at a depth of about 15-30km and 200-400 degrees celsius, making it a difficult rock type to find. Eclogite: the highest grade of metamorphic rock type. Formed by regional metamorphism of igneous rock under very high temperature and pressure. Also typically formed at subduction zones at 45km below the surface, between 400-500 degrees celcius. All of these metamorphic rocks are formed under different temperatures and pressures. Knowing the environment needed to produce each kind of rock can give us a better understanding of the environment it was created, for example, the presence of a subduction zone can be inferred by the type of rock.
orogeny, magmatism and terrane accretion
Orogeny: a term used for a mountain-building event. Leads to a large structural deformation of the Earth's lithosphere. Mainly caused by movement of the tectonic plates, but can be caused by extreme volcanism. Both take tens of millions of years. Noncollisional orogens include subduction. Collisional orogens include convergence (e.g. Himalayan orogeny) Magmatism: the formation of igneous rock form magma. E.g. the formation of volcanoes or island arcs at convergent plate boundaries. Terrane accretion: the main contributor to the growth of continental crust. Although crust is lost by erosion, it is also added to continents at subduction zones by accretion and magmatic events. During subduction, elevated regions within the ocean basin, terranes, are transported toward the subduction zone where they are scraped off of the descending plate and "accreted" to the continental margin. E.x. the Pacific Northwest is a place where terrane accretion is happening today.
The most common mineral groups are:
Oxides: e.g., hematite, corundum Sulphides: e.g., pyrite, sphalerite Sulphates: e.g., gypsum, anhydrite Carbonates: e.g., calcite, dolomite, aragonite, malachite, azurite Silicates: e.g., quartz, feldspars, micas, clays, olivine, amphibole, pyroxene
The Ice Age, or _________ Epoch as geologists term is, lasted from about ____ years ago to _____ years ago
Pleistocene Epoch 2 million years ago until 10,000 years ago
The two most important elements that make up the rocks in the earth's crust, Oxygen (O) and Silicon (Si), form a pyramid structure called an: __________
SiO4 tetrahedron it is actually a pyramid with a triangular shape, envision an oxygen atom sitting in each corner of the pyramid, and a silicon atom sitting in the centre
Define Metamorphic rocks:
formed by transformation of previously formed rocks
crystalline texture, extrusive (volcanic), intrusive (plutonic)
These 3 concepts can be bind by the term "Igneous Rocks", because igneous rocks are rocks that solidify from molten material or magma. These rocks can be categorized in two groups depending whether the cooling of the magma occurred beneath the surface (plutonic rocks) or on the surface (volcanic rocks). We can identify an igneous rock from determining the composition of the rock (minerals) and the texture of the rock. In a shorter sentence, the slower the cooling process of the magma, the larger the crystals on the rock. Volcanic rocks have faster cooling rates and so smaller crystals than plutonic rocks. Crystalline Texture: a rock's inter-grown and interlocking molecular components. The molecules grow in unique patterns. Their size, complexity, and development depend on the rate of cooling. Slow cooking magma form well-developed, larger crystals with more complexity. Textures where the minerals' crystal components are detectable by the unaided eye are referred to as phaneritic. Fast cooling melt will have fewer, smaller crystal formations. Fine textures where the shapes of the mineral components are undetectable by the unaided eye are referred to as aphanitic Extrusive (volcanic) rocks: igenous rocks which have formed from the crystallization of magma above the surface of the Earth. When magma from within the earth flows above earths cool surface, the rocks cool, or "quench", very rapidly. The rapid cooling does not provide sufficient time for large crystals to grow. Therefore, extrusive rocks are characterized by fine-grained textures. Intrusive (plutonic) rocks: Igneous rocks which have formed by the crystallization of magma at depth within the Earth. These rocks are characterized by large crystal sizes, as the cooling process at depth is much slower. The slow cooling provides time for larger crystals to grow and develop complexity.
Fraser Glaciation, non-glacial interval, Pleistocene, Holocene & Quaternary
These concepts are linked by the theme of measuring time and are related by the progression of ice ages and the intervals between them. The Quaternary Period includes the Pleistocene and Holocene Epochs. While the Pleistocene is characterized by being mostly glaciated, the Holocene is considered a non-glacial interval. The Fraser Glaciation is a local example of a glaciation which took place in the Pleistocene Epoch of the Quaternary Period. Fraser Glaciation: The last or most recent of the 3 major glaciations that took place over BC. The Fraser Glaciation started approximately 30,000 years ago and ended 11,000 years ago. It is set in the later part of the Pleistocene Epoch and ended right before the Holocene. This Glaciation period which acted on the Cordilleran ice sheet had a large impact on Vancouver's geology with the sediments it produced. It's influence can also be seen in features like U-shaped Valleys where Capilano River and Lynn Creek begin. Non-Glacial Interval: Also called an interglacial, it's a period of warmer climate between glaciations within an Ice Age. The current Epoch of the Holocene is a non-glacial interval Pleistocene: The epoch that directly precedes the one we are currently in on the geological time scale. It spans from approximately 2 million years ago to the start of the current Holocene Epoch 11,700 years ago. The epoch is known for many cycles of glaciations or ice ages. North America has experiences at least 3 glaciations in this time from, from the earliest Westlynn Glaciation, followed by the Semiahmoo Glaciation and finally the Fraser Glaciation. This Epoch has greatly influences Vancouver's Geology. It can be seen in the ice age sediments that comprise the Fraser Lowland, the erosion and montane shapes in the mountains, the fjords of Howe Sound and Indian Arm or erratic boulders found in odd locations. Holocene: The current epoch of Earth's history which started approximately 11,700 years ago. This Epoch is characterized by a warmer climate which has made it mostly free of glaciation. It is considered an interglacial interval. This interval has seen the build up of sediments that created the Fraser Delta, and the lowlands on which a large part of Vancouver is built. Quaternary: The most recent Period on the Geological time scale. It spans the last 2 million years of the Earth's history and includes both the Pleistocene and Holocene epochs and has seen many cycles of glaciation. We can further situate it in the Cenozoic era that is part of the Phanerozoic Eron.
phyllite, schist, gneiss
These rocks are most common in regional metamorphism. Shale (the "parent rock" of these terms) can metamorphose into phyllite, schist or gneiss depending on heat, pressure and movement. These rocks are of increasing metamorphic grade. These terms are bounded together because they are all foliated metamorphic rocks resulting from regional metamorphism. Phyllite: low-grade metamorphism. Has a corrugated, shiny, slightly green surface. It is made of sericite mica, chlorite and quartz. It is finely grained and has tiny plates of micas causing the reflection of light. Dependent on the direction of pressure during metamorphism, it may crosscut or parallel the bedded rock). Crystals too small to be seen. Schist: medium-grade metamorphic rock, with sheet-like grains that oppose the fine grains of phyllite. 50% minerals such as chlorite and mica. Coarse and distinct. Crystals visible to the eye. Gneiss: high-grade metamorphic rock, subjected to higher temperatures and pressures than schist. Less than 50% of the rock is mineral based. Composes the largest part of the Earth's crust.
arete, cirque, glacial striation, and nunatak
They all have to do with the physical characteristics of glaciers embedded with rocks and/or rugged mountains sculpted by glaciers. Arête: A sharp, narrow mountain ridge or spur, which is normally present above the snowline in mountains sculpted by glaciers Cirque: A half-open, steep-sided hollow on the side of a mountain. It is shaped like a half bowl and is commonly at the head of glacial valley. It is produced by glacial erosion. Glacial Striation: Scratches and grooves cut into bedrock by glacial abrasion from pebbles, gravel etc. embedded in the glacier. Nunatak: A hill, mountain, or peak of rock completely surrounded by a glacier and is projecting above the surface of the glacier or snow.
Quadra sand was overriden and eroded by the Cordilleran ice sheet at the peak of the Fraser glaciation. Before retreating, however, the ice sheet left a later of ____ on top of the sand
Till (a glacial deposit consisiting of stones in a matric of clay, silt and sand)
_________ mark where glaciers stood in the mid nineteenth century at the end of the Little Ice Age. Define.
Trimline the sharp break between the unvegetated zone and the mature forest outside or above it.
Mountain valleys that have been eroded by glaciers typically have __- shaped cross sections (characteristic of mot valleys in B.C) In contrast, mountain valleys in areas that have never been glaciated typically have __-shaped profiles produced by river erosion (such as Lynn and Capilano canyons on the North Shore)
U-shaped V-shaped
How does contact metamorphism occur?
When a hot magma rises up through the crust, the rocks that the magma comes into contact with will be heated up and the heated rocks undergo a transformation.
In many places, the upper limit of a former ice sheet can be inferred from:
a change in the gross character of the landscape - ridges below the limit are typically rounded by glacial erosion whereas those above the limit are sharper and more rugged
The coastline of B.C is indented by fjords. Define.
a deep, long, narrow, steep-walled inlet or arm of the sea along a mountaineous coast. or old river valleys that have been eroded by glaciers and are now flooded by the sea they mark the paths of fast-flowing, highly erosive, outlet glaciers of the former Cordilleran ice sheet
Fjord lake:
a lake occupying a long, narrow, steep-walled valley that has been deeply eroded by a glacier. Fjord lakes occur within and at the front of formerly glaciated mountain ranges. Harrison Lake, Allouette Lake and Pitt Lake are examples
Minerals are the basic building blocks of rocks. The definition comes down to 5 common characteristics:
a mineral is 1) naturally occurring 2) solid 3) inorganic 4) substance that is crystalline 5) has a definite (characteristic) chemical composition
from the definition of a mineral, what does it mean that "a mineral has a definite (characteristic) chemical composition"?
a mineral's composition is not necessarily exactly the same, but it does vary within well-defined limits. We cannot rely on chemical composition composition alone to identify or classify a mineral.
Erratic
a rock fragment carried by a glacier and deposited far from its source. Erratics range in size from pebbles to house-sized rocks
conglomerate, sandstone, siltstone, shale and peat
conglomerate: sedimentary rock composed of rounded fragments of pebbles, cobbles, and/or boulders set in sand, silt or clay which have undergone diagenesis/lithification (i.e sediments deposited on seafloor bury and compact older previously deposited layers which are then exposed to pressure and high temperatures which cause the sediments to become solid rock). sandstone: sedimentary rock composed of sand-sized rock grains/minerals. composed as these small sediments are deposited, accumulated and compacted from intense pressure. the minerals precipitate under the surface, cementing them together. Most often sandstone is tan, brown, yellow or red siltstone: a sedimentary rock composed of silt (silt consists of the minerals quartz and feldspar and it is coarser than clay and finer than sand). Often mistaken for clay but siltstone lacks fissility shale: a sedimentary rock formed when clay and silt are compressed and cemented. composed of mud (mix of clay, tiny fragments of minerals such as quartz and calcite). so fine grained so affected by "fissility" (i.e. the weakness which allows it to be broken along cleavages) The above sedimentary rocks are all differentiated by the size of the grains. peat: partly decomposed plant materials. poor material for foundational use. when buried and heated, peat becomes coal (can be used for fuel).
_________ of sand turns sand into sandstone
diagenesis
A _____ is the seaward end of a glacially eroded valley
fjord
Define Sedimentary rocks:
formed by lithification of surficial deposits, for example, clay, sand or gravel
Define Igneous rocks
formed by solidification of molten rock (magma)
Define shale
lithified clay. Shales are laminated (layered) and can usually be split into flakes.
loess, outwash, till & moraine
the tie that binds these terms together - deposition of glacially-derived materials! These terms are all types of sediments that have been transported and deposited by glaciers. Loess: fine sediment that is transported by wind. Due to its lightness in weight, it can travel great distances, such as over ice sheets to valley bottoms. A thick Loess layer makes soil favorable for agriculture. Loess was deposited over Abbotsford during glacial retreat which is why it has the largest agriculture production in BC Outwash: sediment that is released from a glacier that is melting. The sediment load contains particles as small as clay to large rocks. As the melting glacier water stream carries the sediment, it deposits the heaviest materials first, resulting in the largest rocks being closest to the glacier, and fine sediments are carried to the extent of the water flow. Deposition in this manner is referred to as being "sorted". Outwash plains can be found in the Sumas Mountain-Abbotsford area where a valley glacier retreated 16-12Ma. Till: Similar to "outwash" - the sediment load contains a variety of fine and large material, such as sand gravel, and boulders. But the main difference is that the sediment is unsorted. This is because the sediment is deposited in place, due to the compaction from the weight of the glacier. During glacier retreat, till was deposited in the depressions of the Vancouver area. With the absence of the weight of the glacier, the land began to rise above sea level (glacial rebound). Therefore, till can be found in many upland areas including UBC and the surrounding Point Grey area. Moraine: piles of "till" that have accumulated around the glacier. The type of moraine depends on which part of the glacier it was attached to. Ground moraine: till that has been deposited on a valley floor. Lateral moraine: till carried along the sides of a glacier. When the glacier melts, it forms a ridge along the sides of the valley. Medial moraine: formed by two lateral moraines meeting together at the centre of the glacier. Terminal moraine: till that is found at the farthest advance of the glacier. Moraine is u
Within a mineral class, minerals are further subdivided by:
their crystal structure (structural arrangement of the atoms and compounds in the mineral)
Each glacial cycle ended with rapid climatic warming. Along the BC coast, glaciers retreated inland as sea level rose because of melting ice. In hilly and mountainous areas, the pattern of deglaciation was more complex...
uplands became free of ice first, dividing the ice sheet into a number of valley tongues that retreated separately in response to local conditions
