Terraces are steplike platforms having a gently sloping surface called a 'tread' which is bounded on one side by a steeper ascending slope called a 'riser' or 'scarp'. The riser and tread form the terrace. A narrow terrace is often called a 'bench'.
The creation of terraces or benches is associated with either changes in water levels and resultant wave or water action or, changes in elevation, ie. a rise in land caused by tectonic forces. A combination of both these geomorphic processes often causes the terrace formation.
The Okanagan Valley has a complex underlying bedrock geology consisting of volcanic (igneous) and sedimentary rocks which have been contorted by periods of uplift. The rock formed over millions of years. Of more recent importance is the role glaciation played in the formation of the Okanagan Valley. During the last advance of the large Pleistocene ice sheet, a thick layer of ice covered the present Okanagan and during its advance, sculpted the valley through erosion (e.g., abrasive action). As the ice sheets waned about 12,000 years b.p., a large glacial meltwater lake called Lake Penticton occupied the valley and over the next several thousand years its level subsided in stages. At each stage, a set of terraces (benches) formed by wave erosion along its shoreline. The subsequent terraces are thus like steps going down each side of the Okanagan Valley in this area.
There are six types of terraces and each is formed somewhat differently.
A. Fluvial Terraces - former floodplains of streams or rivers. Changes in elevation or lower water levels cause the abandonment of the higher level floodlplain and a new floodplain formed at the lower level.
B.Kame Terraces - formed at the sides of glacial valleys and are deposits of meltwater streams flowing between the ice and adjacent valley side.
C. Marine Terraces - these types represent former sea or ocean shorelines. (Again, lowering of water levels and tectonic uplift are important.
D.Lacustrine Terraces - these represent former shorelines of nonglacial or glacial lakes. (These are the types of terraces in this area.)
E. Structural Terraces - caused by differential erosion of flat or nearly flat lying layered strata. (Softer deposits stripped from under harder deposits)
F. Travertine Terraces - formed when geothermally heated super saturated alkaline waters emerge to the surface and form waterfalls of prcipitated minerals (eg. carbonates. Think Mammoth Hot Springs in Yellowstone.)
To log this cache answer the following and send responses by e-mail to me. Do not include ansers in your posted log.
1. Suggest why the terraces/benches in this area are not perfectly formed ' treads and risers'.
2. What land uses do you see on the nearby terraces.
3. Lake Okanagan in the distance to the southwest is at 342 m. above sea level. Using the elevation function on your GPS device calculate how far below you in elevation that lake is. (As that lake decreased in size and elevation, many significant terraces were formed including those that local roads occupy, such as Pleasant Valley and L and A.) If you do not have an elevation function, take an educated guess at the drop in elevation.
4. Finally, use the sign information and tell me if the word terraces appears or some other related word. What what was the name of the siphon seen here?
A photo of your visit is not necessary but always welcome. Enjoy the site and views! There is a traditional cache (GC54GPM) also at this location as well as a nearby cache (GC4WGW6) up nearby Foothills Dr. where you can enjoy wonderful views of the Valley and its terraces.
Congratulations to' Bobhoust50' for the First to Visit