Skip To Content
Filter search
Cal Poly Pomona
  • LIBRARY
  • ONLINE SERVICES
  • DIRECTORY
  • MAPS
  • CALENDAR
  • About Cal Poly Pomona
  • Cal Poly Pomona Overview
  • Visitor Information
  • Campus Maps & Tours
  • News
  • Events
  • Administration
  • Annual Security Report
  • Campus Safety Plan
  • Admissions
  • Undergraduate Admissions
  • Graduate Admissions
  • International Admissions
  • Continuing Education Admissions
  • Military & Veterans Admissions
  • Financial Aid & Scholarships
  • Student Accounts & Fees
  • Outreach, Recruitment, & Educational Partnerships
  • Academics
  • Colleges & Departments
  • Majors & Degrees
  • University Catalog & Academic Schedules
  • University Library
  • Research
  • Academic Resources
  • Registrar
  • Campus Life
  • Student Services
  • Student Activities
  • Recreation & Fitness
  • Health & Wellness
  • Housing & Dining
  • Diversity
  • Calendars & Events
  • Campus Safety & Emergency Info
  • Athletics
  • Visit Athletics Website
  • Alumni
  • Visit Alumni Website
  • Giving
  • Why Give
  • Ways to Give
  • Where to Give

PolyCentric University News Center

Main Menu
  • About Our University
  • Admissions
  • Academics
  • Campus Life
  • Athletics
  • Giving
  • Expand/Collapse Menu
Browse: Home / 2010 / March / The Day the Earth Gave Way

PolyCentric

University News Center

Menu

Skip to content
  • About
    • Submissions
    • Contact
    • Department of Strategic Communications
    • PolyCentric
  • News
    • Browse by Topic
    • View All Stories
    • In Memoriam
    • Archives
  • Achievements
  • Announcements
  • Multimedia
    • Videos
    • Photos
  • Social Media Directory
  • Events
  • For the Media

The Day the Earth Gave Way

Posted on March 1, 2010

The Day the Earth Gave Way

Jon Nourse is professor and chair of the geology department.

The recent San Dimas landslide near the 57 and 10 freeways provided exciting opportunities for geology faculty and students to study a real-life example just a short drive from campus. Jon Nourse, professor and chair of the geology department, visited the landslide on Feb. 18 and has been monitoring the cleanup efforts by Caltrans. He shared his insights into the possible cause of the landslide and prevention methods.

Q: What caused the landslide?

A:
Generally, when you have a steep slope, there are forces that make the slope potentially unstable. My main suspicion is it’s something to do with the rainfall, beginning with the storms in December and a couple of big showers in January. The heavy rains must have infiltrated the ground.

Cross section of the San Dimas landslide

Q: Is it normal for landslides to occur several days after the rain and on a warm, sunny day?
A:
Such events have happened before in recent times; for example the Laguna landslide of June 1, 2005. This occurred several weeks after the end of a very wet rainy season. It takes some time for the water to trickle down into the ground. It’s not just soil; there’s also rock but not entirely solid rock. There may also have been a lubricant like clay along an incline fracture. The water pressure could have built up 20 to 30 feet down in the slope, and when the clay got wet, it became slippery. Wet clay is notorious for its low shear strength. With less friction, it’s easier for the mass above the rock area to slide.

Q: How unusual was this event?
A:
This was sort of a random occurrence. The slope had been stable for more than 30 years. There’s usually more danger of landslides during a rainstorm.

Map of the San Dimas Landslide

Q: How can similar landslides be prevented?
A:
A number of methods are used to prevent landslides. The simplest technique is to lower the slope angle in a process called “grading.” Another way is to drain the water from the slope by building a sophisticated drainage system. Sometimes, the top of the slope will be covered with pavement or some sort of impermeable layer that directs the water off to the sides. The water collects at the bottom of the slope in a drainage channel. The most expensive way of stabilizing a slope is to build a retaining wall. You can see these along the 10 Freeway, east of the 57 Freeway. Not only is there a wall, but there are also large rods and bolts that provide reinforced support to the wall and the slope.

Posted in News | Tags answer, Caltrans, connectors, department, faculty, freeway, geology, hillslide, Jon, Jonathan, landslide, nourse, professor, Q&A, question, rain, rainfall, rainstorm, roads, San Dimas, slide, slope, transition, water

POPULAR

  • COVID-19 Mass Vaccination Hub Opening at Cal Poly Pomona

    8666 views / Posted February 4, 2021
  • Newly Launched Vaccination Hub at CPP to Serve Thousands in the Region

    2077 views / Posted February 5, 2021
  • CLASS Dean Iris Levine

    CLASS Act: Dean Levine Sets High Bar for Herself and Others

    760 views / Posted January 11, 2021
  • Budget Brief: Early Exit Program Helps Fill Budget Gap, Prompts Reimagining Work

    695 views / Posted February 23, 2021
  • A group photo of Cal Poly Pomona’s Reading, Advising, and Mentoring Program

    RAMP Receives $2.2 Million Grant For Underrepresented Students

    683 views / Posted January 15, 2021

Picture of the Day »

New Piglets

New Piglets

Cal Poly Pomona in the News »

Interest Surges in Top Colleges, While Struggling Ones Scrape for Applicants

This article was originally published by The New York Times.

Best of the Inland Empire: Best Schools / College


CPP opens mass COVID-19 vaccination site


Cal Poly Pomona opens COVID-19 vaccination site


Cal Poly Pomona Site Capable of Vaccinating Up To 10,000 a Day Opens Friday


Tags
answer, Caltrans, connectors, department, faculty, freeway, geology, hillslide, Jon, Jonathan, landslide, nourse, professor, Q&A, question, rain, rainfall, rainstorm, roads, San Dimas, slide, slope, transition, water
About Cal Poly Pomona Feedback Privacy Accessibility Document Readers

3801 West Temple Avenue,Pomona, CA 91768

©2018 California State Polytechnic University, Pomona

All Rights Reserved