Description
A Science Reader's Guide to CORKS and CORKS in the Crust Parts 1 and 2 are meant to supplement and support the use of E-vents from the Atlantis -- An Expedition to Corks and Vents on the Juan de Fuca Plate, a website developed during an expedition to the seafloor in September, 2007.  Together, the activities, readings, personal accounts and videos on the website will introduce upper level high school and early undergraduate students to the world beneath the seafloor and the methods we use to monitor and measure changes in the crust.  

Additional activities and teachers guides will soon be available at this location.

A Science Reader's Guide to CORKS   View in Flash
Three short articles about CORKS and what they do are provided for background.  The articles were writeen by scientists for scientists and assume the reader has some experience with Earth and ocean science. Each student should, however, experience some success with the readings through the application of the critical reading methods presented. A Science Reader's Guide can be used before or after CORKS in the Crust.  

Time required:  one class period or homework session

Download and print the activity.

CORKS in the Crust: Part 1
Post doc Alison LaBonte' leads students through the analysis of pressure data she downloaded from a CORK during a dive to the seafloor in the DSV Alvin.   Students will note the periodicity and pressure caused by tidal loading, and calculate the ratio between seafloor and formation pressure.  This activity can stand alone or can be used as an introduction to CORKS in the Crust: Part 2.  

Time required:  one class period or homework session

Download and print the activity. 

Answers for Part 1:
1.  A response of 1 day (24 hours) or a half day (12 hours) are both correct.  In actuality, there are two primary period components to this tidal signal, a semidiurnal tidal signal (period = ~12 hours, frequency twice per day), and diurnal tidal signal (period = ~24 hours)
2.  27.0425 - 27.0125 = 0.030MPa = 30KPa = 30000Pa.  The maximum change in water height in this record is 3 meters.
3.  TIDES
4.  A reduction in volume of pore spaces when the crust is squeezed will result in increased pressure. 
5.  The pressure change in pore spaces of relatively incompressible material, such as the ceramic block, that results from applying the same squeezing force will be less. This is because the reduction in volume of the pore spaces will be much less when you squeeze a stiff block than when you squeeze a sponge.  
6.  Example. Measured high tide (@ ~12pm 02/22) to low tide (@ ~ 6pm 02/22) oscillation.  Change in formation pressure = 90KPa; change in seafloor pressure = 28.5KPa. Loading efficiency is 28.5KPa/90.0KPa = 3.16KPa. Materials with a higher compressibility will have a higher loading efficiency.  Additional info: The maximum possible loading efficiency is 1, describing the case where 100% of the squeezing (or loading) pressure applied to the material is transferred to the fluids in the pore spaces.
7.  The results should be the same to within +/- 0.1.  The compressibility of the crust is the same throughout the duration of this record (1 week) and if you were to look at a longer record, you could see compressibility is the same over many years.

CORKS in the Crust: Part 2   View in Flash
Part 1 provided an introduction to fluid pressure data.  In this exercise, students will link this data to measurements collected by other systems to draw conclusions about seismic events on the Juan de Fuca. Grad student Katherine Inderbitzen wrote these exercises between dives in DSV Alvin to service CORKS near the Juan de Fuca Ridge.  This activity requires some knowlege of earthquakes.

Time required:  one class period or homework session

Download and print the activity.

Answers for Part 2:  
1.  Amplitude jumps following the seismic event, then decays to background levels over time.
2.  The compressional component dominates, resulting in an increase in pressure following the earthquake.
3.  Yes, it will be lateral flow as opposed to vertical flow.  This may increase the level of crustal alteration as pressurized fluid is forced into the formation as opposed to flowing more passively through the crust.
4.  Drainage of the fluid in the formation (after the initial pressure increase due to fluid being forced into the crust).
5.   Well-connected.
6.  Potentially persists for many kilometers, however we do not completely understand its limitations.  One idea is to look for alteration minerals like sulfides in old oceanic crust.  

Middle Valley
1.  Middle Valley has a negative fluid transient (which persists over time), whereas Endeavour has a positive fluid transient that decays quite rapidly.  This tells us that the Middle Valley event resulted in a net dilatation of the porous crust. 
2.  Remember that there was a net dilatation of the crust.  The pore space created was likely filled with seawater and not magma.  If magma had been injected into the crust, there would likely have been increased hydrothermal venting in Middle Valley as a response to an additional heat source.