A day at the racetrack
This lesson aims to solve the mystery of the sliding rocks of the Racetrack Playa in Death Valley - a unique and fantastic phenomenon
Key questions
Where is Racetrack Playa?
What processes could be responsible for the Sliding Rocks?
Where is Racetrack Playa?
Racetrack Playa is a seasonally dry lake (a playa) located in the northern part of the Panamint Mountains in Death Valley National Park, California, USA. Death Valley is near the western border with Nevada, and is approximately 300km from Los Angeles. It is one of the many desert basins within the Sierra Nevada Mountains.
What processes could be responsible for the Sliding Rocks?
Early investigators explained the phenomenon as the result of the rocks being embedded in an ice sheet in the coldest storms of winter. Being 1,131 metres above sea level, the playa receives snow which freezes to a layer of ice at times. Ice rafts can form and it was thought that they could move across the playa lake with the rocks embedded in them. However, experiments to set up similar phenomena in 1996 did not fully support this theory. In 1998 investigators during an abnormally strong El Nino year with ice-sheets, did not show any movement of rocks from their mapped locations. Nevertheless, further measurements using very accurate GPS measurement instruments have found that there is a general movement trend towards the north-north east, which is the same direction that the prevailing winds move towards. Therefore, winds are the most likely cause of the trails in some way. The rocks seem to be propelled by the winds which have been made much stronger by being channelled through corridors in the south.
Images copyright Noel Jenkins and shared under a Attribution-NonCommercial-ShareAlike Creative Commons license unless stated otherwise
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Starter
Look at the gallery. What is unusual about the rock? Has this rock moved? How has it moved? Think of some ideas.
Nobody has ever witnessed or filmed the rocks moving.
These rocks are located in Death Valley, California ,USA.
Main Activity
The gallery shows one of the mysterious sliding rocks.
In pairs or in groups work out the reasons for why these rocks mysteriously move by solving the mystery 'Why does the rock move?'
You can also watch a YouTube video showing the Racetrack in wet conditions. It might give you a clue or might it be a red herring?
Plenary
As a group present your ideas on why the rock moves to the rest of the class.
Use evidence from the mystery cards to back up your ideas as well as the images.
Groups can challenge each other's theories to arrive at a consensus, or agreement, on why this rock moves.
Early investigators explained the phenomenon as the result of the rocks being embedded in an ice sheet in the coldest storms of winter. Being 1,131 metres above sea level, the playa receives snow which freezes to a layer of ice at times. Ice rafts can form and it was thought that they could move across the playa lake with the rocks frozen into them.
However, in 1998 during an abnormally cold winter with ice-sheets, the rocks did not move.
Using very accurate GPS to track the rocks, investigators have found a general movement trend towards the north-north east, which is the same direction that the prevailing winds move towards.
Therefore, winds are the most likely cause of moving the rocks. The rocks seem to be propelled by the winds which are made much stronger by being channelled through corridors in the south.
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