Question: For what is the mountain that has Thayer Glacier on the east slopes popular ? 

Context paragraphs:
Mount Gannett: Mount Gannett is a 9649 feet peak in the Chugach Mountains of eastern Alaska, United States, located 50 miles east of the city of Anchorage.  It was named by Lawrence Martin of the U.S. Geological Survey in 1911 for Henry Gannett.  One arm of the Knik Glacier flows from the ice fields of Mount Gannett's north and east slopes, and the Colony Glacier rises on the west and southwest slopes, flowing into Inner Lake George.  In between, the Gannett Glacier flows down a narrow valley northwest of the summit to join the Knik Glacier.  The mountain has an estimated topographic prominence of 4300 feet .

Three Sisters (Oregon): The Three Sisters are a complex volcano of three volcanic peaks of the Cascade Volcanic Arc and the Cascade Range in the U.S. state of Oregon.  Each exceeding 10000 ft in elevation, they are the third-, fourth-, and fifth-highest peaks in the state of Oregon, and are located in the Three Sisters Wilderness, about 10 mi south of the nearest town of Sisters.  Diverse species of flora and fauna inhabit the area on and around the mountains, which is subject to frequent snowfall, occasional rain, and extreme temperature differences between seasons.  The mountains, particularly South Sister, are popular for climbing and scrambling.

Thayer Glacier: Thayer Glacier is in the U.S. state of Oregon.  The glacier is situated in the Cascade Range at an elevation of over 8000 ft .  It is on the east slopes of North Sister, an extinct shield volcano.

Vidul Glacier: Vidul Glacier (Bulgarian: "ледник Видул" , ‘Lednik Vidul’ \'led-nik 'vi-dul\) is the 7.5 km long and 1.4 km wide glacier on the east side of the main crest of northern Sentinel Range in Ellsworth Mountains, Antarctica.  It is situated northwest of Skaklya Glacier and southwest of the middle course of Newcomer Glacier.  The glacier drains the north slopes of Mount Reimer and the east slopes of Mount Dawson, flows northwards and joins Newcomer Glacier west of Mount Warren in Gromshin Heights.

Delyo Glacier: Delyo Glacier (Bulgarian: "Дельов ледник" , ‘Delyov Lednik’ \'de-lyov 'led-nik\) is the 8 km long and 2.7 km wide glacier on the east side of the main crest of north-central Sentinel Range in Ellsworth Mountains, Antarctica.  It is situated northwest of Rumyana Glacier and south of Burdenis Glacier.  The glacier drains the north slopes of Mount Giovinetto and the east slopes of Mount Viets, flows northeastwards and together with Burdenis Glacier and Gerila Glacier joins upper Ellen Glacier north of Bruguière Peak.

Chocolate Glacier: Chocolate Glacier is located on east slopes of Glacier Peak in the U.S. state of Washington.  The glacier descends from 10400 ft to 5900 ft and is partially connected to Cool Glacier which lies to its south just below the summit of Glacier Peak.  As is true with all the glaciers found on Glacier Peak, Chocolate Glacier is retreating.  Chocolate Glacier retreated approximately 1380 m between 1906 and 1946, however during a cooler and wetter period from about 1950 to 1979, the glacier advanced 450 m .  Chocolate Glacier has resumed retreating since and has given back 350 m , nearing its previously recorded minimal length.

North Guardian Glacier: North Guardian Glacier is located on east slopes of Glacier Peak in the U.S. state of Washington.  The glacier descends from 8600 ft to 6430 ft and is partially connected to Chocolate Glacier which lies to its south.  As is true with all the glaciers found on Glacier Peak, North Guardian Glacier is retreating.  North Guardian Glacier retreated approximately 1500 m between 1850 and 1946, however during a cooler and wetter period from about 1950 to 1979, the glacier advanced modestly.  Since then North Guardian Glacier resumed retreating and thinning and by 2005 the glacier had returned to its minimum length as recorded in 1946.

Cool Glacier: Cool Glacier is located on east slopes of Glacier Peak in the U.S. state of Washington.  The glacier descends from 10200 ft to 6900 ft and is partially connected to Chocolate Glacier which lies to its north just below the summit of Glacier Peak.  As is true with all the glaciers found on Glacier Peak, Cool Glacier is retreating.  Cool Glacier retreated approximately 1500 m between 1850 and 1946, however during a cooler and wetter period from about 1950 to 1979, the glacier advanced.  Since then Cool Glacier resumed retreating and by 2005 the glacier was within 40 m of its minimum length recorded in 1946.

Sabazios Glacier: Sabazios Glacier (Bulgarian: "ледник Сабазий" , ‘Lednik Sabazios’ \'led-nik sa-'ba-ziy\) is the 19 km long and 6 km wide glacier on the east side of northern Sentinel Range in Ellsworth Mountains, Antarctica.  It is situated south of Newcomer Glacier, west of Anchialus Glacier, north of Embree Glacier, and east of Zhenda Glacier and Skaklya Glacier.  The glacier drains the east slopes of Mount Alf and Mount Sharp, and the north slopes of the side ridge that trends 9.15 km from Mount Dalrymple on the main crest of Sentinel Range east-northeast to Robinson Pass, flows northwards and joins Newcomer Glacier northwest of Mount Lanning in Sostra Heights.

Zhenda Glacier: Zhenda Glacier (Bulgarian: "ледник Женда" , ‘Lednik Zhenda’ \'led-nik 'zhen-da\) is the 8 km long and 4.8 km wide glacier on the east side of the main crest of northern Sentinel Range in Ellsworth Mountains, Antarctica.  It is situated west of Sabazios Glacier and southeast of Skaklya Glacier.  The glacier drains the northeast slopes of Mount Sharp and the east slopes of Mount Barden, flows northeastwards and together with Skaklya Glacier joins Sabazios Glacier west of Mount Lanning in Sostra Heights.

Supporting paragraphs: Thayer Glacier Three Sisters (Oregon)
Answer: climbing and scrambling.