_Kimberly Dike._ The low bluff across the river is formed by a vertical dike of basalt which is about 60 feet wide. This dike cuts through the John Day Formation and, farther north, the Picture Gorge Basalt (Fig. 8 ). It crosses the river valley diagonally and can be traced nearly four miles. The dike is formed of once-molten rock that “froze” in a fissure which was a channelway for lava that fed a flow on the earth’s surface. Many similar dikes are visible along the road east of Kimberly. The basaltic magma is believed to have originated at depths of 40 miles or more within the part of the earth called the mantle. (At 105.3 turn east on State Highway 402 along the North Fork of the John Day River) [Illustration: Fig. 8.—Basalt dike two miles south of Kimberly.] K. 5.0 _Basalt Dike._ A basalt dike 15 feet wide cuts basalt flows in bluffs north of the road and forms a wall 20 feet high in places; it is visible also across the river. L. 11.2 _Parallel Dikes._ Two prominent parallel dikes, among others, form crests of hogbacks south of the river. A small tapering dike cuts pink and white beds of the John Day Formation in the river bluff. This dike is the southwest end of an irregular intrusive mass of basalt in which the river has cut a steep-walled gorge. M. 13.2 _Basalt Intrusion._ The road is cut through 300 feet of basalt intruded into the John Day Formation. Both contacts are well exposed. The basalt—when molten—baked and reddened 3 to 6 inches of the adjacent beds. (At 13.9 the highway crosses the North Fork of the John Day River and follows the Cottonwood Creek Valley.) N. 18.0 _Irregular Dikes._ Above the highway several small irregular basalt dikes cut the white beds of the John Day Formation. Parts of the largest dike are 10 to 15 feet high. O. 20.1 _Cottonwood Creek Valley._ The view northwestward down Cottonwood Creek toward Monument (Fig. 9) exemplifies the development of broad valleys by erosion in soft beds of the John Day Formation under the gently warped Picture Gorge Basalt. To the south, the valley ends against massive rocks of the Clarno Formation which were raised as a block by movement along the Hamilton fault. The red beds are in the lower part of the John Day Formation. Note the contrast between the irregular massive intrusion in the valley bottom west of Monument and the thin regular basalt flows. [Illustration: Fig. 9.—Northwest view down Cottonwood Creek toward Monument.] On your right, the irregular contact between the John Day Formation and Picture Gorge Basalt reveals an ancient landscape buried under lava flows (Fig. 10). Some of the flows wedge out against former hillsides and one, marked by the dry falls, fills an old valley.