Know before you go: This EarthCache can be completed at any of Point Pleasant's beaches.
Materials Recommended for the Earthcache:
- Measuring tool
- Magnet
What is continental sand?
Continental sand, as its name says, is the most dominant sand type on continental beaches. We are probably all (with few exceptions) very familiar with this buff grainy material that is mostly composed of quartz but may also contain other minerals like feldspar, mica, and biogenic grains. However, none of them are not nearly as abundant as quartz.
How is continental sand made and transported to beaches?
Rocks erode or weather over a long period of time, mainly by water and wind, and their sediments are transported downstream. These sediments continue to break apart into smaller pieces until they become fine grains of sand. The type of rock the sediment originated from and the intensity of the environment gives different compositions of sand. The most common rock to form sand is granite, where the feldspar minerals dissolve faster than the quartz, causing the rock to break apart into small pieces. In high energy environments rocks break apart much faster than in more calm settings. The term for sand formed by weathering is epiclastic.
Composition of Sand on the East Coast:
Quartz Sand:
Quartz is the most important sand-forming mineral because it is resistant to both physical and chemical weathering. Sand that is enriched in quartz is likely old (matured) and has traveled far from the source area, sometimes thousands of kilometers. A long journey is required to allow weathering to break down weaker minerals that were initially present in the rocks.
Mineral grains that make up this kind of sand can be very old. They may have broken away from their source rocks millions or even hundreds of millions of years ago and have perhaps seen many weathering cycles.
Figure 1: Quartz sand is usually clear or white in color.
Feldspar:
Feldspar is the most abundant mineral in the Earth’s crust. This group of silicate minerals is somewhat hard, is often pink, white, or grey in color.
Figure 2: This sand contains traces of feldspar (they are the pink grains in the sand).
What is ironsand:
Ironsand is a type of sand with heavy concentrations of iron. It is typically dark grey or blackish in color. It is composed mainly of magnetite, Fe3O4, and also contains small amounts of titanium, silica, manganese, calcium, and vanadium.
Where is ironsand found?
Ironsand is found worldwide. Although the iron mineral composition of the ironsand is mostly magnetite, the sand is usually mixed with other types of sand that wash downriver or ashore from mountainous or underwater deposits. The exact composition of the sand mixture may vary drastically even in the same geographic region. In some areas, the sand may contain mostly quartz, while in others the sand may be made primarily from volcanic rock such as basalt, depending on the types of minerals along the water's path. The ironsand is typically picked up along the way from beds, veins, or inclusions of magnetite, which may originate a great distance from the sand deposits, and washed downstream or along the currents with the rest of the sand. Being heavier than the other sands, it is often deposited in areas where the water experiences a sudden change in direction or speed, such as the widening of a river or where the waves ebb and flow against the shoreline.
Sand Sizes:
Sand is divided into five categories based on its size:
-Very fine sand (1/16 – 1/8mm)
-Fine sand (1/8 – 1/4mm)
-Medium sand (1/4mm – 1/2mm)
-Coarse sand (1/2mm – 1mm)
-Very coarse sand (1 mm – 2mm)
These are accurate measurements according to the Udden-Wentworth Scale
Logging Tasks:
-
What is the color and composition of the sand that you observe on the beach? What minerals are present?
-
Scour the beach for a dark patch of sand. Using a magnet, is some of the sand here classified as ironsand? Why or why not?
-
Based on your observations, does the sand at Point Pleasant contain,
-
0% of ironsand
-
1-10% of ironsand
-
10-30% of ironsand
-
>30% of ironsand
-
Estimate the size of the sand on the beach. Using the Udden-Wentworth scale, what category are most of the grains of sand of the beach a part of?
-
As of June 2019, earthcaches are now allowed to have a required photo logging task. Please provide a photo of yourself, your GPSr, or a personal item that proves that you have visited this site. Please post this in your log.
Congrats to xxSubSeaxx for the FTF!
Enjoyed finding this EarthCache? Consider awarding it a favorite point!
Sources:
https://en.wikipedia.org/wiki/Sand
https://en.wikipedia.org/wiki/Ironsand#United_States
https://www.sandatlas.org/continental-sand/
| We have earned GSA's highest level: |
 |
