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Yosemite and Sequoia & Kings Canyon are parks in transition. They have long been geologic wonderlands, rarities that recently ran headlong into myriad social concerns. Now the National Park Service, environmental groups, and various watchdogs are all taking a serious look at the parks' futures.

The Landscape

Towering sheets of granite. Lush forests that give way to emerald meadows blanketed in wildflowers. Views that stretch farther than some countries and make visitors feel like they are standing on the edge of the world. The varied landscapes of these parks are memorable, to say the least. Yosemite has an almost bizarre conglomeration of sheer granite monoliths and wide-open spaces. Sequoia & Kings Canyon have trees that are as wide at the base as some homes, along with wildflowers in almost every patch of sun. All these wonders occur because of the area's astounding geological nature.

About 300 million years ago, layers of sediment that had been building up on the ocean floor were forced under the emerging North American continent. The process created such intense heat that the sediment became molten magma, some of which erupted via volcanoes. Where it chilled and hardened before reaching the surface, the magma created huge slabs of granite.

This process continued intermittently for about 150 million years, forming a large mountain range roughly parallel to the West Coast -- the Sierra Nevada. For the next 55 million years, wind and water ate away at the volcanoes and sedimentary rock, sweeping it into California's Central Valley and leaving mountains of exposed granite.

Scientists theorize earthquakes along the present-day San Andreas Fault began forcing the eastern edge of a landmass beneath the Sierra upward 25 million years ago, eventually tipping west, raising tall mountain peaks. In Yosemite, the upheaval raised the park's eastern range to 11,000 feet, while in Sequoia & Kings Canyon, it created the ominously barren and beautiful Kaweah Ridge, also known as the Great Western Divide, which ranges from about 11,000 to 14,000 feet in elevation.

As rivers raged through the valleys, they carved deeper and deeper into the earth, eroding the bedrock. Great canyons were formed, and when the earth's temperature cooled about 3 million years ago, glaciers covered the Sierra Nevada. These fields of ice tore at the granite, expanding and contracting with such force that they carved deep valleys, slicing granite walls vertically into the steep U-shapes of Yosemite Valley and Kings Canyon.

When the glaciers melted, they left behind steep mountains smoothed by ice, along with piles of debris that dammed the flow of rivers, creating lakes in the valleys. The rest of the landscaping took place in an evolutionary blink of an eye. Over the course of 10,000 years, sediment, swept down from above, filled these lakes. Meadows were formed, and then came wildflowers, followed by trees, and eventually people.

You can still see glaciers in Yosemite, near Tuolumne Meadows. Also check out the glaciers on Yosemite's Mount Lyell, Mount Dana, and Mount Maclure. The glaciers here were probably formed about 2,500 years ago but are quickly receding today.

Glaciers are responsible for the variety of rock formations in the parks. There are spires, domes, sheets, and arches. Yosemite has cornered the market for number and diversity, offering one or more of each within the span of an easy 3-mile walk. Most of the unusual rock landmarks here were created by fractures within the rock. These fractures occur vertically, horizontally, and at an incline. Called joints, they represent the weakest point of a rock and a point that has already been broken. The type of joint most common in Yosemite, and also evident in Sequoia & Kings Canyon, is sheeting. Concentric joints -- fractures that seem to occur along curved lines -- form after years of increasing and decreasing pressure from overlaying rock. When pressure decreases, the granite expands upward and breaks or fractures off in sheets, similar to peeling an onion very slowly.

Erratic boulders are another common sight. These large rocks were originally located elsewhere but were transported and plopped down haphazardly -- again, probably by glaciers.

Ridges of rocky deposits are called moraines, left behind as glaciers recede. The best place to see moraines is in Yosemite, en route from Tuolumne Meadows to Tioga Pass.

In Sequoia National Park, Moro Rock is a dome towering 6,725 feet above sea level. Moro Rock's summit offers breathtaking views of the Kaweah Ridge, with some peaks rising to 14,000 feet.

Kings Canyon National Park boasts North Dome, above Cedar Grove. Some people with a vivid imagination say it resembles Half Dome. North Dome is not accessible by car or on foot.

Waterfalls hang over the Yosemite Valley like a sparkling diamond necklace. The valley boasts three of the world's tallest waterfalls. Upon entering the valley, you'll spot the 620-foot Bridalveil Fall first. It looks large, but that's because you haven't seen the rest of the cast.

The real biggie is Yosemite Falls, close to Yosemite Lodge. The fall appears to be one drop but is, in fact, a set of waterfalls that measures a combined 2,425 feet. Lower Yosemite Fall drops 320 feet, Upper Yosemite Fall descends 1,430 feet, and a cascade in the middle makes up the difference.

To the west of El Capitan you'll find Ribbon Fall, which drops an uninterrupted 1,612 feet to the valley floor but is often dry in summer.

The longest single fall in Yosemite is Sentinel Fall. It drops 2,000 feet from the west side of Sentinel Rock, directly across the valley floor from Yosemite Falls. To view this waterfall, walk back toward El Cap and make an about-face -- it's one of the geology-obscured views in the park.

Up the valley are a series of dramatic staircase falls accessible only on foot. Vernal Fall and Nevada Fall occur just a half-mile apart along the same river.

Waterfalls in Sequoia & Kings Canyon are less numerous but still impressive. Mist Falls, in Kings Canyon, is beautiful but requires a 4-mile hike. This wide waterfall near Cedar Grove is up a rushing creek, which includes several large cascades.

Below is Roaring River Fall, a length of waterfall also accessible only on foot; it flows from Cloud and Deadman canyons. Garlic Fall, in the Monarch Wilderness area just outside Kings Canyon, can be viewed from the Yucca Point overlook on CA 180.

Note: Most waterfalls are fed by snowmelt and rely on winter runoff to survive. In late summer, many of them (including Yosemite Falls) dry up.

Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.