Study Notes for GEOL 101: Waves and Currents

The course focuses on the foundational concepts of geology, emphasizing the understanding of oceans, waves, and currents.

The objectives for mastering this section of GEOL 101 include:
- Communication: Ability to articulate concepts related to ocean waves and currents.
- Data Synthesis & Quantitative Skills: Skills necessary to analyze data related to oceanography.
- Exploration of Physical Formation: Understanding how the ocean waves and currents form and move.
- Predictive Skills: Being able to predict the motion of objects within ocean currents and comprehend the Coriolis Effect.

Initial Wind Interaction:
- Wind starts moving over calm water.
- Wind applies shear stress to the water surface, creating movement.
Surface Tension:
- Water stretches and pulls at the surface, similar to a sheet being tugged.
Formation of Ripples:
- As wind continues to interact with water, ripples form.
Wave Development:
- Wind can push against the sides of these ripples, causing them to evolve into bigger waves.
Gravity's Role:
- Gravity pulls larger waves back down, creating vertical motions at a specific location (up and down movements).
Physical References:
- Refer to pages 690-691 for further details on wave concepts.

A thought experiment involving a cork floating in water illustrates the behavior of these objects:
- The cork bobs up and down instead of moving with the wave direction, demonstrating wave motion characteristics.

Wave Movement:
- Time 1 vs. Time 2: The position of water molecules is analyzed to understand their behavior.
- Key Definitions:
- Amplitude: The height of the wave from the midpoint to the crest.
- Wave Height: Double the amplitude.
- Wavelength: The distance between successive crests or troughs.
- Wave Base: The point below which water molecules are not influenced by wave movement.
- Illustration shows that beneath the wave base, water molecules don't move up and down.

Formation and Behavior:
- Rip currents occur when ocean waves hit the beach and create strong ocean-ward forces.
- If caught in a rip current, the recommended action is to swim parallel to the shore to escape.

Map of Surface Currents:
- Various currents include:
- East Greenland Current
- West Greenland Current
- North Atlantic Current
- Alaska Current
- California Current
- North Pacific Current
- Gulf Stream
- Florida Current
- Japan (Kuroshio) Current
- And more as indicated on the map of ocean currents.
- The coloration on the map indicates temperature, with red representing warm currents and blue cold currents.

Wind Shear:
- Wind shears across the water surface initiating currents.
Coriolis Effect:
- Rightward deflection in the northern hemisphere and leftward in the southern hemisphere.
Pressure Variations in Water:
- Analyses show how these forces interact to generate large-scale surface currents.

Deflections Explained:
- In the northern hemisphere:
- Northward-moving objects veer to the right.
- Eastward-moving objects veer to the right.
- In the southern hemisphere:
- Southward-moving objects veer to the left.
- Westward-moving objects veer to the left.
- Angular Velocity: All points on the Earth have the same angular velocity, rotating 360° per day, yet linear velocity decreases toward the poles.

Prevailing Winds:
- At lower latitudes, winds typically flow from east to west, combining this with the Coriolis Effect will dictate the movement of gyres such as the North Atlantic Gyre.

Inward Spiral Formation:
- The winds and Coriolis Effect lead to an inward spiral effect on water.
Water Mounding:
- This spiral causes accumulation or a mound of water at the center.
Pressure Differences:
- The elevation difference results in a pressure difference, pushing surrounding water outward.
Circular Flow:
- When the forces balance, water flows in a circular path around the mound, maintaining the current dynamics.

Definitions:
- Downwelling: Water flow towards the shore resulting in vertical descent due to gravity when the flow cannot go upwards.
- Upwelling: Occurs when the surface flow moves away from the shore, allowing deeper water to rise and fill the void, bringing nutrients to the surface and fostering biological activity.
Mechanisms:
- Generally caused by shore-parallel winds.
Illustrations show the mechanics of both downwelling and upwelling, including subsurface currents impacting biological life.

Influencing Factors for Upwelling and Downwelling:
- Temperature and salinity changes can alter water density, facilitating the processes of upwelling (less dense water rising) and downwelling (denser water sinking).

Global Implications:
- Ocean water may take hundreds to thousands of years to complete a cycle through thermohaline circulation.
- This is established as a global-scale "conveyor belt" that circulates water, mixing the ocean in approximately 1,500 years.

Event Overview:
- In 1992, a shipping crate containing 28,000 plastic bath toys fell overboard, leading to unexpected lessons about ocean currents.
Tracking Outcomes:
- The following years saw landfalls of the toys at various global locations, providing insight into ocean drift and circulation patterns based on historical data.

Throughout the study of ocean currents and wave mechanics, understanding the interplay of physical forces is essential for comprehending ocean dynamics. The principles outlined provide a foundational guide for further exploration in geology and oceanography.