Bumpty Bumpty Bump EarthCache
Hidden : 1/23/2013
Difficulty:
1.5 out of 5
Terrain:
1.5 out of 5

Size: Size: other (other)

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Geocache Description:


Bumpty Bumpty Bump

Ever since the Moorpark to Simi Valley Freeway connector was opened on October 15th, 1993, I’ve wondered why the section between Collins Drive and Madera Road was so bumpy. CalTrans has repaired this section of the freeway numerous times, but the bumps keep coming back.

So just what causes these bumps? The 118 freeway crosses the middle Sespe Formation, which is replete with what are referred to as "red" and "blue" beds. You've no doubt noticed them. Because of the strike and dip of the Sespe Formation (strike northeast-southwest and dip 30-40 degrees to the northwest), the beds cross under the freeway diagonally somewhat on end. Unlike the predominately sandy strata of the Sespe, the red and blue beds are high in clay. When they get wet, they expand; lifting whatever is on top, at least the first two or three feet. So, up goes the concrete pavement on the road with each winter, cracking the concrete and providing a very exciting ride for vehicles on the road. If you're traveling west on the freeway, your right front wheel goes up first, followed shortly by your left front when wheel, then by your right rear wheel, and then by your left rear wheel. Going down the other side of the bump, is the opposite of that same twisting effect. If you watch the beds in the road cut, you will pass them, and then be twisted. This is because of the northeast-southwest strike of the beds. When the beds dry out to some degree, the road does flatten somewhat, but never goes back to where it was before the road was paved.

The Sespe Formation in this area, is a non-marine deposit from a tropical forest environment of Eocene/Oligocene age, about 24 million years old and younger as you go west. The red and blue beds are "overbed" strata formed when the river flooded adjacent river valley and deposited its clay load. In the process, small animals and occasionally large mammals were drowned. Mice, for example, were drowned in their burrows. As a result, the Sespe Formation in this area has produced about half of the recorded vertebrate fossils known for the Oligocene period.

If you don't see evidence of the clay beds from the GZ, you may want to take a short drive between the Collins Dr. and Madera freeway off-ramps on Easy St., which is the 118 freeway frontage road.

Logging requirements

If you're part of a group, each member must provide their own unique answers to these questions.
Do not post your answers in your log.
Please send me email (not a message) with:

  1. The text "Bumpty Bumpty Bump" on the first line.
  2. The number of people in your group.
  3. From the GZ, look to the east, down the freeway heading into Simi Valley. Describe what you see as the freeway crosses the Sespe Formation. Do you see any evidence of the clay beds? If so, what do you see?
  4. Do you think it is possible to permanently flatten out the freeway?
  5. Why are there so many vertebrate fossils in the area?
  6. Optional: Post a picture of yourself, or your group, at the GZ.
  7. Just For Fun: What is the origin of the term "Bumpty Bumpty Bump?"

Additional Hints (Decrypt)

Cnex ng gur arneol Cnex & Evqr, gura jnyx gb gur TM nobir gur serrjnl.

Decryption Key

A|B|C|D|E|F|G|H|I|J|K|L|M
-------------------------
N|O|P|Q|R|S|T|U|V|W|X|Y|Z

(letter above equals below, and vice versa)


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