Virtual Field Trip to Jesse Jones Park

Dear Students,
On April 3, 2020 I went to Jesse Jones Park with my trusty field assistant (aka my husband, Kevin) to examine the features at and round Spring Creek. Below are some photos and videos to help you better "read" the landscape around streams and recognize the features created by streams.

Stop #1 was along the Cypress Boardwalk trail. This swamp is filled with bald cypress tress and other plants that can tolerate having their "feet" wet for long periods of time.

Here I discuss the wetland a bit. This wetland is most likely an oxbow lake; however, it is hard to determine that from the

Teaching students how to learn - tutoring https://www.youtube.com/watch?v=oxdeFvTrP9k
Metacognition is the key to acing chemistry - https://www.youtube.com/watch?v=yGBfd7LeGMM

Plate Tectonic Mechanism

The mechanism for plate tectonics is generally accepted to be a combination of convection currents in the mantle coupled with ridge push and slab pull. The poorly understood part includes 1) to what depth are the convection cells active, 2) are there several layers of convection cells or only one, 3) is the lithosphere the upper part of the convection cell or a passive participant, 4) to what degree to slab-pull and ridge-push move the plates, among others. Below are two images showing how the convection cells in the upper mantle may be configured.

Figure 3: Plate Tectonic mechanism showing that the oceanic plate shown in the diagram is a passive participant in the convection cell. It is moved through convection traction as well as slab pull and ridge push (Earle, Steven, BC Open Textbook)

Figure 4: Plate Tectonic mechanism showing that the oceanic plate shown in the diagram is an active participant in the convection cell. The lithosphere forms the top of the convection cell. Ridge push and slab pull are also playing an important role. (Earle, Seven, BC Open Textbook)

The Silicate Minerals - Building blocks of rocks

Modified from Rocks and Minerals, The Silicate Minerals -- by Anne E. Egger, PH.D.

As we discussed in class, a mineral is a naturally occurring, inorganic, crystalline solid with diagnostic physical properties and a definite chemical composition. Rocks are typically composed of minerals although there are exceptions. As is always the case in nature, our definitions often do not cover all of the variables that are seen in nature. Some materials formed through geological processes are not composed of minerals yet are still considered rocks. Examples include obsidain and coal. We will be concentrating on rock-forming minerals as well as a few of the common accessory minerals found in the rocks we will be learning about. The mineral quartz (SiO2) is and example of a very common mineral. It is found in all rock types and in all parts of the world. It occurs as sand grains in sedimentary rocks, as crystals in both igneous and metamorphic rocks, and in veins that cut through all rock types, sometimes bearing gold or other precious metals. It is so common on Earth's surface that until the late 1700s it was referred to simply as "rock crystal." Today, quartz is what most people picture when they think of the word "crystal."

Quartz falls into a group of minerals called the silicates, all of which contain the elements silicon and oxygen in some proportion. Silicates are by far the most common minerals in Earth's crust and mantle, making up 95% of the crust and 97% of the mantle by most estimates. Silicates have a wide variety of physical properties, despite the fact that they often have very similar chemical formulas. At first glance, for example, the formulas for quartz (SiO2) and olivine ((Fe,Mg)2SiO4) appear fairly similar; these seemingly minor differences, however, reflect very different underlying crystal structures and, therefore, very different physical properties. Among other differences, quartz melts at about 600° C while olivine remains solid to temperatures of nearly twice that; quartz is generally clear and colorless, whereas olivine received its name from its olive green color.

Minerals and their Physical Properties

This week our lab is on the identification of minerals using their physical properties (lab handout, mineral chart, flow chart.) Minerals are an important natural resource. Everything we use that is not grown, is derived from the Earth. These resources include rocks, minerals, and hydrocarbons to name a few. Therefore, understanding where to find these resources is rather important. Common mineral uses include (from http://www.mii.org/commonminerals.html):

1. Gypsum:  Processed and used as prefabricated wallboard or as industrial or building plaster, used in cement manufacture, agriculture and other uses.
2. Feldspar: A rock-forming mineral, industrially important in glass and ceramic industries, pottery and enamelware, soaps, abrasives, bond for abrasive wheels, cements and concretes, insulating compositions, fertilizer, poultry grit, tarred roofing materials, and as a sizing (or filler) in textiles and paper. Albite is a feldspar mineral and is a sodium aluminum silicate. This form of feldspar is used as a glaze in ceramics.
3. Fluorite (fluorspar): Used in production of hydrofluoric acid, which is used in the electroplating, stainless steel, refrigerant, and plastics industries, in production of aluminum fluoride, which is used in aluminum smelting, as a flux in ceramics and glass, and in steel furnaces, and in emery wheels, optics, and welding rods.
4. Halite (Sodium chloride--Salt): Used in human and animal diet, food seasoning and food preservation, used to prepare sodium hydroxide, soda ash, caustic soda, hydrochloric acid, chlorine, metallic sodium, used in ceramic glazes, metallurgy, curing of hides, mineral waters, soap manufacture, home water softeners, highway deicing, photography, herbicide, fire extinguishing, nuclear reactors, mouthwash, medicine (heat exhaustion), in scientific equipment for optical parts. Single crystals used for spectroscopy, ultraviolet and infrared transmission.
5. Kaolinite: Also known as "china clay" is a white, aluminosilicate widely used in paints, refractories, plastics, sanitary wares, fiberglass, adhesives, ceramics, and rubber products.

The Layered Earth

Everything we see in geology can be directly or indirectly related to Plate Tectonics. If we played the six degrees of separation game, called it Six Degrees of Plate Tectonics, we would rarely go over three degrees before the answer came back somehow relating to Plate Tectonics. It truly is a unifying theory!

The reason that the earth's plates move is in large part due to the fact that our Earth is layered. It wasn't always layered. When debris first accumulated making the protoEarth, it was a fairly homogeneous rock orbiting the sun. Once it reached a critical mass, however, the gravitational energy accumulated caused the entire earth to melt into a fiery ball of liquid hot magma! This event is called the Iron Catastrophe. Catastrophe in this sense does not refer to a tragic event but rather to the classical, Greek-derived definition which is the culminating act in a drama. The Iron Catastrophe lasted between 100 m.y. and 500 m.y. and was the culminating act in the Earth's drama. It created the layered Earth we have now: a core made of iron and nickel, a rocky mantle that is high in iron and magnesium and poor in silica, and a rocky crust that is rich in silica and other lighter elements such as calcium, carbon, nitrogen, oxygen, sodium, aluminum, etc.

Three centuries ago, the English scientist Isaac Newton calculated, from his studies of planets and the force of gravity, that the average density of the Earth is twice that of surface rocks and therefore that the Earth's interior must be composed of much denser material. Our knowledge of what's inside the Earth has improved immensely since Newton's time, but his estimate of the density remains essentially unchanged. Our current information comes from studies of the paths and characteristics of earthquakes waves travelling through the Earth, as well as from laboratory experiments on surface minerals and rocks at high pressure and temperature. Other important data on the Earth's interior come from geological observation of the Solar System, its gravity and magnetic fields, and the flow of heat form inside the earth.

Carbonate Sedimentary Rocks

Carbonates
The carbonate sedimentary rocks are those rocks composed primarily of calcite. This includes all of the limestones. Limestone are chemical sedimentary rocks because the calcite was carried to the ocean or lake or sea in solution. The calcite then precipitated directly from the water to for the sediment or crystals that make up the rock. These sediments are NOT transported to the basin as particles like is the case with the siliciclastics. These sediments are created in the basin in which they are found. For example: a bioclastic limestone is composed of skeletal grains formed of calcite. This calcite was precipitated by the organism. Later, the organism died and its skeletal remains became part of the ocean bottom. That sediment was buried under more skeletal debris, compacted, and cemented together to form the bioclastic limestone we later see.

Carbonates have two possible origins (biogenic or chemical inorganic) and two possible textures (clastic or crystalline:

1. biogenic origin - the grains that make up the rock were created by an organism and deposited on the basin floor when the organism dies. Most of these rocks have a clastic texture. The exception to this rule are reef rocks and stromatolites (calcite deposited by cyanobacteria).
2. chemical inorganic origin - the grains that make up the rock were created inorganically, that is, without the help of an organism. The texture of such rocks is often crystalline with the exception of oolitic limestone. The ooids are created when a grain of something (sand, shell fragment, ooid fragment, etc.) rolls around on the bottom of a warm shallow sea and calcite precipitates on that grain as thin layers in a similar manner as pearls are formed. These ooids are later buried and cemented together to form a rigid framework = clastic texture.

Photomicrograph of modern ooids from a beach on Joulter's Cay, The Bahamas. Scale bar for size. Photo by Mark A. Wilson (Department of Geology, The College of Wooster)

Ooids on the surface of a limestone; Carmel Formation (Middle Jurassic) of southern Utah, USA. Scale bar for size. Photo by Mark A. Wilson (Department of Geology, The College of Wooster)

Photomicrograph of  thin slice of calcitic ooids from the Carmel Formation, Middle Jurassic, of southern Utah, USA. Scale bar for size. Photo by Mark A. Wilson (Department of Geology, The College of Wooster).

https://ore.exeter.ac.uk/repository/handle/10871/17081 <--parrot fish article

 In my opinion, it is best to study the siliciclastics together and the carbonates together to start. Then try to tell the siliciclastics apart from the limestones.

Chert
Chert is off on its own because it is neither a siliciclastic nor a carbonate. Chert is formed by the recrystallization of siliceous skeletal grains such as radiolarian tests, diatom tests, and sponge spicules; or, through the replacement of previously existing material. Limestones are often replaced by chert. Petrified wood is chert. The cellulose in the wood is replaced, molecule by molecule, by chert. Therefore, it can be difficult to tell the origin of chert without field relations. Because all chert is recrystallized, either directly from pore waters or by the replacement of some other substance, it is considered to be chemical inorganic.  Note the conchoidal fracture that chert displays. This fracture pattern is what allows chert (aka flint) to be napped to form arrowheads, spearheads, scrapers, etc.

Stone tools made from chert.

Study hard, get to know the rocks, and you will do well on the test. Good Luck!!