PERMISSION:
This Earthcache is placed with permission of the Chief of Resource Education, Great Smoky Mountains National Park.
EARTHCACHE REQUIREMENTS:
Each cacher must send in their own answers when logging this find. Review the materials below and answer by message/email the questions to the best of your ability. Questions are listed after the lesson. Please follow all logging requirements and do not post any answers with your log.
ABOUT CLIFF BRANCH FALLS:
Cliff Branch Falls is a roadside waterfall located along Rt. 441 on the North Carolina side of the Great Smoky Mountains National Park. There is parking across from the falls which will allow viewing without crossing the road to obtain the needed observations to meet the needs of this earthcache. Be aware, at all times, of traffic in either direction. Please note, that access may be limited to this section of 441 if the GSMNP closes it due to weather conditions. Please use Leave No Trace ethics during your presence and maintain your safety.
While most of the rock formations within the Great Smoky Mountains National Park are sedimentary, there are a multitude of other rock types located in different areas of the park. These mountains were created millions upon millions of years ago...at least 245 to 310 million years . There are numerous reference materials, books and information available at the GSMNP Visitor Center locations and of course, your knowledgable Park Rangers, are also a valuable resource for other information.
IGNEOUS ROCKS:
Igneous rocks form when hot, molten rock crystalizes and then solidifies. This melt begins deep within the Earth, close to active plate boundaries, then rises towards the surface. Igneous rocks are divided into two groups, extrusive and intrusive, dependent upon where the molten rock solidifies. Extrusive Igneous Rock is formed when magma exits then cools above or close to the surface of Earth. These are rocks that originate at eruptive volcanoes and oozing fissures. The magma cools and solidifies quickly when exposed to the comparatively cooler temperatures of Earth's atmosphere. This quicker cooling doesn't allow mineral and crystals time to grow. Therefore, those rocks generally have a very fine-grained or glassy texxture. Intrusive Igneous Rock is created when magma is trapped deep inside Earth. Large blobs of molten rock rises towards the surface of Earth. Some of this magma can "feed" volcanoes on the surface, but the majority remains trapped beneath the Earth's surface. This magma that is trapped eventually cools over thousands to millions of years until it reaches a solid state. This slow cooling allows individual mineral grains an extended period of time to grow, resulting in a relatively large physical size. Intrusive rock has a coarse grained texture.
SEDMIENTARY ROCKS:
Sedminentary rocks are formed near or on the surface of Earth. They are caused by gradual, but constant, natural changes in the environment. Contributing factors to sedimentary rock formation includes erosion, precipitation or natural weathering, as well as lithification and dissolution. These environmental happenings eat away at dirt or rock surfaces slowly and wash sediments together that eventually collect and build up into rock formations. Some of the most common types of sedimentary rock include sandstone, shale, limestone and coal. In each case, debris, organic materials or minerals slowly form into what are typically soft, dry and porous rock types.
METAMORPHIC ROCKS:
Metamorphic rocks started out originally as some other type of rock, however, changed from their original form. Metamorphic rocks form when rocks are subjected to very high heat and pressure, hot mineral rich fluids or a combination of these. These conditions are located deep within the Earth or where tetonic plates meet. The metamorphism process does not melt the rock, but does transform them into dense, compact rocks. As a result, new minerals are formed either by the rearrangement of the mineral's components or metamorphosed rock into new and different shapes. They often appear as smeared, folded or flattened looking. Despite those conditions, metamorphic rock does not endure hot enough temperatures to trigger them to melt, otherwise they would be igneous rocks. Metamorphosed sandstone, siltstone and shale are the most common type in the Great Smoky Mountains National Park.
SANDSTONE - Sandstone is a clastic sedimentary rock composed mainly of sand-sized silicate grains. Sandstones comprise about 20-25% of all sedimentary rocks. It is composed of quartz or feldspar (both silicates) because they are the most resistant minerals to weathering processes at the Earth's surface. Rock formations that are primarily composed of sandstone usually allow for th percolation of water or other fluids and are porous enough to store large quantities, making them valuable aquifers. Quatz-bearing sandstone can be changed into quartzite through metamorphism, usually related to tetonic compression within orogenic belts.
SILTSTONE - Siltstone is a clastic sedimentary rock composed primarily of silt. If is a form of mudrock with a low low clay mineral content which cah be distinguished from shale by its lack of fissility. Fissility, in geology, means the ability or tendency for a rock to split along flat planes of weakness, sometimes referred to as parting surfaces.
SHALE - Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mixture of flakes of clay, minerals and tiny fragments of other minerals, especially quartz and calcite. Shale is characterized by its tendency to split into thin layers called laminae, less than one centimeter in thickness with a resulting property known as fissility. Shale is the most common sedimentary rock. Shale typicall will exhibit varying degrees of fissility. As as result of the parallel orientation of clay mineral flakes in shale, it breaks into thin layers, very often splintery and normally parallel to the otherwise indistinguishable bedding planes. Non-fissle rocks of similar composition and particle size are described as mudstones or flaystones. Rocks with similar particle sizes but less clay (>2/3 silt) and are grittier than siltstones.
BIOLOGICAL WEATHERING:
Weathering refers to any process by which a rock is broken down, generally at surface level. Biological weathering refers to weathering caused by organisms such as plants, fungi, bacterial microorganisms or animals. It can be either physical or chemical. Biological weathering can work with physical weathering by weakening the rock or exposing it to physical forces or chemical weathering. Not all biological weathering is visible. Many microorganisms in the soil or on the rock's surface can contribute to this. Many types of bacteria obtain their nutrition through a combination of nitrogen from the surrounding air as well as minerals. These minerals may include silica, phosphorous and calcium from the rock. This rock is weakened from this removal and is further vulnerable to break down into smaller rock particles or new minerals. Weathering is the first step in the erosion process, which breaks down the three majow the three major rock types found near the Earth's surface: sedimentary, igneous and metamorphic.
FREEZE/THAW WEATHERING:
Some of these rocks have experienced free/thaw weathering. Water will expand 9-10% in a frozen state. This makes the free/thaw cycle incredibly powerful. As water seeps into these tiny cracks and freezes, the expanding force of the ice created from this freezing will cause the rock to crak a bit more. With each future freeze/thaw, this crack will become longer and wider due to the wedge action of the water as it freezes. Through this mechanical process, over a vast number of years, the rock continues to split as the increasing volume that is able to seep into the crack, freezing and thawing, expanding the crack, eventually causes a complete separation.
WHAT IS A WATERFALL?
A waterfall occurs where a river or a strem flows over a large step in the rocks and loes elevation. Over a period ofyears, even thousands to millions, the edges of this shelf will gradually break away and the waterfall will steadily retreat upstream, ccreating a gorge or recession. As a stream flows, it carries sediment. The sediment can be a microscopit silt, pebbles or even boulders. Sediment can erode stream beds made of softer rock such as sandstone or limestone. Eventually the streams channel cuts so deep into the stream bed that only a harder rock, such as granite remiains. Waterfalls develop as these granite formations form cliffs and ledges. Often, the rock stratum just below the more resistant shelf will be a softer type, meaning undercutting, due to splashback, occuring here for form a shallow cave-like formation known as a rock shelter or plunge pool under and behind the waterfall. Eventually, the outcropping, more resistant cap rock will collapse under pressure to add blocks of rock to the base of the waterfall. These blocks of rock are then broken down into smaller boulders by attrition as they collide with each other. They also erode the base of the waterfall by abrasion, creating a pluge pool. A stream's velocity increases as it nears a waterfall, increasing the amount of erosion taking place. The movement of water at the top of the waterfall can erode rocks to be very flat and smooth. Rushing water and sediment topple over the waterall, eroding the plunge pool at the base. The crashing flow of the water may also create powerful whirlpools that erod the rock of the plunge pool.
CLASSIFYING WATERFALLS:
There is not a standard way to classify waterfalls. Some scientists classify waterfalls based on the average volume of water in the falls. Another popular way to classify waterfalls is by width, whicle others classify by height. One of the most popular, if least scientific, ways to classify waterfalls is by type. A waterfall's type is simply the way the waterfalls descends. Most waterfall fit more than one category. The types are:
BLOCK - water descends from a relatively wide stream or river
CASCADE - water descends a seris of rock steps
CATARACT - a large waterfall
CHUTE - water traveling through a very narrow passage, forcing water through at an unusually high pressure
FAN - water spreads horizontally as it descends while remaining in contact with the bedrock
HORSETAIL - descending water maintains some contact with bedrock
MULTI-STEP - a series of waterfalls after another of roughly the same size with its own sunken plunge pool
PLUNGE - water descends vertically, losing contact with the bedrock surface
PUNCHBOWL - water descends in a constructed form, then spreads out in a wider pool
SEGMENTED - distinctly separate flows of water form as it descends
SLIDE - water glides over a single slab of rock maintaining a smooth continuous contact
TIERED - water drops in a series of distinct steps or falls
VEIL - water travels over rocks creating a thin layer of water that just barely covers it's surface
RESOURCES:
Mountain Geology, Great Smoky Mountain National Park, 2022 edition
QUESTIONS TO BE ANSWERED:
1. Which form of weathering do you think has had the greatest impact on the rocks at this location and why?
2. Based on the description of the different types of rock groups, which group do you feel is the best discription of rocks present at this falls?
3. Looking at the falls, what type of falls best describes what you are looking at and is there a visible plunge pool?
4. Describe your weather conditions at the time of your visit and if you see evidence of potential freeze/thaw weathering.
5. Optional, but appreciated, is a photograph posted with your log of the falls or surrounding area. You do not have to be in the picture unless you want to.
GINGIN'S MESSAGE:
C - Calming of the senses as the fall offers nature's reassurance
L - Listening to the sound of rushing water, so quiet yet so loud
I - Intently flowing from the hills to the river....a journey without end
F - Friends or family to enjoy this spot together or in one's own solitude
F - Feeling the crisp mountain air on a chilly morning or the sun's warmth in summer
B - Beautiful falls with a flow that waxes and wanes as the seasons change
R - Respecting the land, the wildlife, the water and the air for today and future generations to come
A - Admire what you could easily miss if you weren't being keenly aware of your surroundings
N - Nature sharing her creations...this falls, surrounding forest and waters that flow through it and wildlife dependent on it for survival
C - Constantly changing with each passing season, from icy winters to wildflower springs
H - Help through Leave No Trace to keep this falls stunning hundreds of years from now
F - Flowing quickly from the falls then meandering when it joins the river
A - Always remove signs of our presence, except footsteps and memories
L - Longing to spend a bit more time at this spot to appreciate it's splendor
L - Living and loving the moment here, for each is numbered
S - Satisfaction in knowing you've done your best to protect this National Park and other public lands through your actions...make them all good ones.