The Red Pyramid is the third largest pyramid in Egypt after the Pyramids of Khufu and Khafre at Giza. At 105m high, it looms impressively over Dahshur. Built c.2950 BC it is Egypt's first true pyramid.
Geological overview of the site:
The necropolis of Dahshur is located approximately 30 km south of Cairo. The necropolis belongs to the extensive burial fields of the Memphite region, all constructed during the Old and Middle Kingdoms. The monuments of the necropolis are located on the Egyptian Limestone Plateau, close to the floodplain of the river Nile. The geology of the area mainly consists of Pliocene and Eocene sandstone and limestone. These formations are repeatedly intercalated with fossil banks (oysters and nummulites) and by shale or sandy shale. Fluvial sediments (mainly well-rounded pebbles and coarse sand) belonging to a former river system – the so-called Protonile which occupied the present-day Nile basin in the early Pleistocene – built a relict river terrace at the western margin of the study area. In the middle Pleistocene the Pronile, also a predecessor of the present-day Nile, deposited fluvial sediments in the east closer to the present-day floodplain of the river Nile. These sediments (were deposited directly on top of the Eocene bedrock. The fault system of Egypt was laid out in Mesozoic times. During that time Egypt comprised two main structural units: a) an unstable shelf to the north with NE-SW transcurrent faults and fault-bounded basins, and b) a stable shelf in the south mostly covered with Palaeozoic and Mesozoic continental deposits. The area belongs to the former region of the unstable shelf. The pyramids were constructed using two main building materials: The core material of the pyramids between Abu Roash and Meidum was mined in the direct vicinity of the respective pyramid location. By contrast, the casing material consists of a high quality white limestone which originates from the eastern bank of the river Nile between Gebel Mokkatam and Helwan. Thus, the availability of building material was an important factor for the choice of the setting. It has been assumed that the ancient architects conducted feasibility studies of potential pyramid locations to check the stability of the underground and the availability of suitable building material for the core of the monuments. Furthermore, infrastructural factors such as accessibility to the Nile floodplain and facility of transporting allochthonous building material were evaluated before an area was chosen. To reduce the amount of earth works or mining activity, geomorphological structures such as wadi beds were preferred as connecting paths between the construction area and the floodplain of the Nile.
The landscape surrounding the necropolis of Dahshur comprises two major landscape units: a) the escarpment, and b) the floodplain of the river Nile. The escarpment mainly consists of Pliocene and Eocene limestones and Eocene sedimentary rocks. All of the site is covered by well-rounded pebbles corresponding to Pleistocene Nile deposits. In the northern part of the site, the escarpment is defined as a sharply delimited linear structure. South of the pyramid ruin of Amenemhat III, the linear appearance of the escarpment is disintegrating. The transition zone from the escarpment to the floodplain of the river Nile is widely covered by sand sheets extending 100-150 m from east to west.
(taken from Bebermeier, Wiebke & Alexanian, Nicole & Blaschta, Dirk & Ramisch, Arne & Schütt, Brigitta & Seidlmayer, Stephan. (2011). Analysis of Past and Present Landscapes Surrounding the Necropolis of Dahshur. Erde. 142. 325-352). I would reccomend reading the full article for a complete geological overview.
To log this earth cache you have to answer the following questions. These can be found through researching the geology of the site, and judgements made visiting the site. To find this cache you will need to enter the pyramid, which is quite the adventure but also physically challenging.
1. Who built the pyramid?
2. To the nearest degree, what is the slope angle of the stones?
3. What stone is the core of the pyramid made out of?
4. Now largely gone, what type of stone was the facing of the pyramid made out of?
5. Estimate the height of the rock cut passage descending into the pyramid.
6. Describe the vaulting of the burial chamber
7. Estimate the size of the blocks used for the construction of the pyramid
8. With your answers 3 and 7, estimate the weight of each block.
Optional extra: Take a photo with your gps at the pyramid.