Natural Bridges Field Trip Guide

By Christie Rowe and field partners "Caffeine" and "Salty Snacks"

Figure 1: a Sea Arch carved out of the Santa Cruz Mudstone at Natural Bridges State Beach (Picture source:

1. Introduction

Natural Bridges State Beach is a small but beautiful park at the western end of West Cilff Drive in the city of Santa Cruz. The park gets its name from sea arches and sea stacks formed of the Santa Cruz Mudstone which mark the beach (MBNMS website). The rocky shelf just west of the beach contains structures which can be interpreted to reveal some of the tectonic history of the location. This field trip will focus on measuring some of these structures (joints and small faults) and interpreting their orientation to find the paleostress directions. (This information came from the instructor. So don't forget to ask for it!) In addition, there are interesting depositional and tectonic structures in the rocks which fall outside the scope of this exercise but are well worth seeing and examining. So keep an eye out!

For this field trip, everyone will need to bring: