Cabo San Lucas Rocks! A Geological Tour of the Sea of Cortez by Doreena Patrick
Aaah my Journeys…It wasn’t too hard to figure out where I was taking y’all next…
I looooove maps…When I was a kid, I used to find any atlas I could, any road map, any mobile travel guide or any map guides to National parks and especially Disney!!!
Of course, I never did quite get the knack of refolding the road maps 😊
I still by a new road atlas every year, some roads change or are added!!!I love tracing the veins of roads stretching across the maps, imaging the places. And I have been fascinated by exploring where no roads have been carved into the wilderness.
One of the places I always dreamed of going to by far was the Sea of Cortez or more specifically Cabo San Lucas. I used to look at the remoteness of the Baja in comparison to the rest of Mexico and to the tip of the Baja peninsula and think one of these days!!
Well I travel a lot and it really is my passion. I can feel the angst that I need to get moving and sometimes I just get in the car and drive. But you can’t drive to Cabo, but then again you can but I’d rather get to the Cabo Wabo Cantina as fast as I can 😊. (There’s my bar reference 😊) So, for a good deal of my adventures I end up on a plane (yes and maybe a bar)!
The vistas in Cabo are breathtaking to say the least. There are too many pictures for me to put on this post but suffice it to say this locale needs to be on your list!! I consider it my nirvana, a cross between the paradise of Hawaii and the majesty of the Southwestern deserts!
When I am flying, I always choose a window seat, especially when I am flying west. And you know the journey sometimes is better than the destination (not in this case though).
If we are flying below the clouds, I start by taking in the feathery coastlines of the east, the subtle rising of the old weathered Appalachians, every meandering river system, and the flat green and rolling plains of the Midwest. If the flight is taking a northern route, I can’t wait identify the Missouri breaks, the winding Mississippi and if I am really lucky, I spot the Badlands of South Dakota before we turn south and catch the first glimpse of the majesty of the Rockies. If it so happens the flight is taking a more southernly route, we may catch a glimpse of the vast Chesapeake Bay before we turn southwest and move down through the backbone of the Appalachians and then veer even further southwest towards the Gulf of Mexico luckily getting small glimpses of the crystal blue waters overlaying the hidden gem of the carbonate platform below. We continue along the immense southern Texas plains, across the barren landscapes of New Mexico (my next journal entry😊), then taking in the diverse, colorful Arizona landscape, hoping for a glimpse of the Granddaddy of them all the Grand Canyon.
For this journey, as we steer south, the blue waters of the Sea of Cortez appear on the horizon and I know that I only have about 800 more miles to the Cabo Wabo Cantina….oops I mean the tip of the Baja Peninsula.
As we start our descent onto the peninsula, the stark vast desert appears, reminiscent of my trips to southern Arizona, the Tombstone area, Chiricahua, Tucson, the saguaro cactus etc… and that is because it is the same!!! The only thing separating these vast deserts is the Sea of Cortez!!
What are the geological processes at work that created this desert paradise? …I am glad you asked 😊
The Baja California Peninsula separates the Pacific Ocean from the Gulf of California. This jutting peninsula extends 775 miles from the northern city of Mexicali, to Cabo San Lucas, in the south. The narrowness of the peninsula can easily be seen from the air, ranging from 25 miles at its narrowest to 200 miles at its widest point.
The Baja sits squarely in the “horse” latitudes. (Named aptly by sailors as to where their horses died due to no water). These latitudes, due to the large Hadley cells circulation in the atmosphere, produces warm, dry, and sunny conditions and are the main cause for the existence of the world’s major deserts including the four main deserts on the Baja peninsula; the San Felipe Desert, the Central Coast Desert, the Vizcaíno Desert and the Magdalena Plain Desert.
So now to the geology 😊
The Gulf of California is the boundary of the North American plate and the Pacific plate. These plates form what is known as a transform fault where they are sliding along each other and, in some areas, stretching (the Fault Block regions). Baja California sits over the infamous San Andreas fault stretching from the Gulf into the heart of California. The latest theory is that the Baja California peninsula was formed as the fault shifted northward splitting from the mainland of Mexico only about 6-10 Mya and slowly forming the enchanting Sea of Cortez.
The varied region of the Baja cannot be explained simply but it can be broken down into 5 regions based on geologic landforms. These are: the broad flat coastal plains, the isolated coastal mountains, the fault block mountains and alluviated dry river valleys of the Basin and Ranges, and the plateaus of the Volcanic Tablelands. Our focus is on the Land’s End, the beaches and craggy hilltops of the Cabo San Lucas area and the much-photographed Sea arch or more commonly known as El Arco.
During the Late Jurassic to early Cretaceous (150 to 62 Mya: the “end of the dinosaurs”) the first three regions formed (coastal plains, coastal mountains and the fault block mountains) and were part of the formation of the collision of the North American and the Pacific Plate (Farallon Plate). This Pacific plate slammed (ever so slowly) into the western sliding North American plate. The Pacific plate slowly subducting under the Atlantic plate and nudging the Atlantic plate to the Northwest and incidentally starting the volcanism in the infant Rocky Mountains and eventually forming the transform fault systems of California.
This subduction zone throughout the Cretaceous and into the middle of the Cenozoic (Miocene) generated several mountain building episodes known as Orogenies (Nevadan-Middle Jurassic, Servier-Late Jurassic, and Laramide-Cretaceous). During these orogenetic events, volcanism occurred but also deep magma chambers crystallized and formed a structure known as a batholith. A batholith is a very large igneous intrusion of solidified magma typically producing a granite. In western North America these granite batholiths extend from Southern Alaska to the “end of the world” at the tip of the Baja.
The batholiths of the Baja are from the same forces that shaped the Sierra Nevada batholiths (mountain chain). How the land contorted and stretched creating what us geologist lovingly called the Basin and Range region of North America is hotly contested still but suffice it to say that subduction forces to the west caused extension forces within the Basin and Range region, stretching and thinning the crust. These forces led to isostatic uplift of blocks and down dropped valleys. As the land was contorting and stretching it formed the tilted granitic fault block ranges, we see towering over us on the beaches.
As these fault-block granitic mountains rose, the forces of weathering and erosion of the soft rocks above the granites eventually exposed the hard-core center after millions of years. Some of the batholiths still remain buried but the ones that jut out into site are the ones that give us the “exotic” terrain we see throughout Cabo.
Climbing through the nooks and crannies of Lover and Divorce beaches (Yes I sure did, bathing suit and all 😉)of the beach rocks one clearly sees the beautiful pink and white granites sparkling in the sun…Quartz, K-Feldspar, Muscovite…And if you look really closely you see weathering spots on the rocks, where slowly the treasure trove of minerals are eroding to create the beautiful sparkling sand beaches of the Cabo region. Walking along these beaches is little like mining 😊 the washes of the Arizona desert😊
Aaaah the Arch you may ask!!! Most of the pictures I posted are mine. But no matter, what angle, or panorama you take, the photos can’t capture the majesty of this striking place. I certainly did cry when the small boat brought me almost close enough to touch the Arch and catch a glimpse of the Pacific meeting the Sea of Cortez. 😊
Generally, sea arches form when powerful waves are deflected to the sides of what is called the headland. These waves eventually erode and compromise the rock creating weakness on both sides and an eventual “hole” in the rock is exposed. Eventually, the Pacific met the Sea of Cortez developing from these powerful surge channels. The supporting roof of the arch is known as the “keystone” but alas these types of structures only last decades to maybe centuries collapsing into sea stacks etc…Oh wow!! I have to quick get back there El Arco, Cabo and Cabo Wabo is calling!!
Dr. Patrick is an industry-known geochemist, chemostratigrapher and geologist with a specialty in Rare Earth Elements (REE) Geochemistry. For more information on her services, please call 817-952-1850 or email her directly: dr.patrick@vvinnovation.com