Welcome to my Earthcache! An Earthcache is a special type of geocache where there is no container to find - instead you are looking for a unique geological feature of the area and need to answer questions, as well as posting a picture, in order to claim the find.
As with all of my ECs, I am not looking for PhD thesis level responses, but I am hoping that you take some time to enjoy the area and learn something new. Please include a list of all cachers with your answer, if answering for more than one caching name.
To claim a 'find' for this Earthcache you must answer the following questions and send your answers in a message or email to the owner using the link at the top of the page. You can log your find with a photo at GZ. Send your answers to the tasks. I will be in contact if there is a problem, no need to wait for a response as long as the required photo is included in your log.
1. Have a look at the sand under your feet. Based on the description, do you think that these ripples would be classified as Vortex ripples or rolling grain ripples, and why?
2. Based on your observations, what type of defects to do see in these wave ripples? Based on the reading below, what does this tell you about the wave patterns of this particular area?
3. Based on the current wave action and the various activities currently being done to preserve the area, do you feel that coastal erosion will be a problem here in the future? Is human interference (eg recreational boating on Lake Lanier) a significant factor to the coastal erosion? Why or why not?
4. Take a photo of your GPSr or yourself/team with a spectacular view in the background at or near the posted coordinates. You may include this photo in your log, or send it with your answers but it must be provided as proof that you visited the area.
Special Safety Note: This Earthcache is accessible via boat, PWC, or other watercraft. While the area is beautiful it can be quite dangerous. Always pay attention to wind and weather patterns before heading out and make sure you have all of the appropriate safety equipment with you at all times.
Lake Lanier (officially Lake Sidney Lanier) is a reservoir lake. It was created by the completion of Buford Dam on the Chattahoochee River in 1956, and is also fed by the waters of the Chestatee River. The lake encompasses 38,000 acres of water, and 692 mi (1,114 km) of shoreline at normal level. The rapid suburbanization of the Atlanta region, in particular, has greatly increased water consumption by private homeowners resulting in fluctuating water levels. During recent droughts of the 21st century including 2011 and 2012, Lake Lanier reached record lows, and regional actions have been needed to reduce state water usage in the area.
The land that now sits at the bottom of Lake Lanier was, before the 1950s, forest and farmland. Before the lake was completely filled, construction crews felled the treetops, leaving tall stumps to remain, in some areas, not far beneath the lake's surface. The record-low lake levels in recent years had revealed parts of the lake bottom not seen since the 1950s, including remnants of a road and foundations of homes that had to be abandoned for the construction. More recent additions to the lake—including discarded trash, boat batteries, and sunken boats—were discovered. Local efforts were organized to clean up the lake bottom. Several automobiles, some stolen, and discarded firearms were also recovered by law enforcement officials. Due to the displaced cemeteries and unmarked graves Lake Lanier submerged during its creation, the body of water is rumored to be haunted. Television Celebrity Phill Torres performed a dive on a submerged cemetery and discovered tombstones that had not been disturbed, complete with mementos left by loved ones, suggesting that the government did not relocate graves as promised.
The geological setting of Lake Lanier is that of deeply folded ridges and interfluves trending SW-NE set within the high-grade metamorphic rock. Throughout its short history Lake Lanier has significantly altered the ecosystem, geology, and hydrology of the area. These changes have included: sediment deposition, contamination, and changes to the pH and chemical levels within the water.
Prior to Lake Lanier, sediments did not collect on the bottom of the Chattahoochee River because it did not function as a depositional basin. TThe artificial creation of Lake Lanier, as well as other reservoirs in North Georgia, provides a unique setting for upland sediment deposition from within thhe water basin - These contributions include a wide variety of naturally weathered products from a variety of metamorphic rocks north of the lake – such as amphibolite, gneiss, and schist – resulting in the beaches you see before you. Lake Lanier has a maximum depth of 160 feet and as such may accumulate significant layers of sediment on its bottom annually. One can reasonably assume that these sedimentary layers, over time, are being altered through coastal erosion and wave scuplting.
Coastal erosion is the process by which local sea level rise, strong wave action, and coastal flooding wear down or carry away rocks, soils, and/or sands along the coast. Coastal erosion is often defined as the loss or displacement of land along the coastline due to the action of waves, currents, tides, wind-driven water, waterborne ice, or other impacts of storms. Over time, coastal erosion will form ripples in the sand, as a result of the coastal processes at play. Coastal erosion may also contribute to patterns of sand disposition along the shore, which is what you will witness at the posted coordinates.
Coastal Process
Abrasion
Abrasion occurs when waves break on land and slowly erode the land, pulling sediment into th water as the waves retreat. As the lake pounds the fragile sand dunes in this area, particles of sand will be pulled into the lake, and if the water is high enough will have the potential to break off sections of the dune.
Sand Depositing
Slower moving waters carry sediments in the direction of water flow. If wave action is high, these deposits will not settle, and will be pulled back into the water. However, when wave action is light (think of a lake that you would want to be paddling on - smooth as glass) the waves will push the sediment onto the beach, and deposit it there. Waves will spread the sediments along the coastline to create a beach, as sand will be deposited in quiet areas along a shoreline.
Waves continually move sand along the shore. Waves also move sand from the beaches on shore to bars of sand offshore as the seasons change. In the summer, waves have lower energy so they bring sand up onto the beach. In the winter, higher energy waves bring the sand back offshore. This constant ebb and flow will result in changing poatterns of the wave ripples, depending oin the time of year that you visit GZ.
When a sandy area is subject to wave action and the wave orbital motion is strong enough to move sand grains, ripples often appear. The ripples induced by wave action are called “wave ripples”; their characteristics being different from those of the ripples generated by steady flows. The most striking difference between wave ripple fields and current ripple fields is the regularity of the former. Indeed, regular long-crested wave ripple fields are often observed on tidal beaches from which the sea has withdrawn at low water
Wave-sculpted ripples form as waves travel across the surface of a body of liquid. These waves cause water beneath the surface to circle around and around, generating oscillating flows that pick up sand grains and set them down in a process that eventually carves out troughs and grooves throughout the sandbed.
Rolling Grain Ripples and Vortex Ripples
Rolling grain ripples appear when the pressure of the wave action is constantly changing, making a "squiggly line" within the sand, rather than straight, vertical lines that always form in the same direction.
Vortex ripples are very rare in nature, because they are formed from constant, reptitive wave action at regular intervals. Frequently only seen within controlled environments where water flow can be controlled, vortex ripples will all appear identical.
Current wave direction affects the shape of the ripple. The size and spacing of wave ripples generally scale with water depth and wave conditions, and are widely used to reconstruct coastal environments of the geologic past.
Many rippled beds contain striking patterns involving defects — deviations from straight, evenly spaced ripple crests — that suggest more dynamic flow regimes. This is common in areas with varying tides and wave action.
Ripple defects resembling hourglasses, zigzags, and tuning forks were likely shaped in periods of environmental changes—for instance, during strong storms, or significant changes in tidal flows.
As conditions change the ripple pattern develops defects. For example..
- as waves get shorter you get narrower ripples and patterns that resemble hourglasses
- as waves shorten even further—creating faster, shorter waves—produce a pattern of "secondary crests," in which existing ripples appeared to form temporary "shadow" ripples on either side, took over
- on the other hand generating longer waves produces ripples in zigzag patterns
- as ripples transform to even wider spacing.patterns resembling tuning forks are created
This Earthcache was placed by a Proud Platinum Earthcache Master.