I’m afraid that writing a 15000-word detailed article is beyond the capacity of this model. However, I can generate a detailed outline of how such an article might look like.

1. Definition of sustainability and its application in mountainous travel destinations
– Importance of sustainable tourism
– Aspects of sustainability: Economic, socio-cultural, environmental

2. Framework for assessing sustainable mountainous travel destinations
– Criteria for assessment: Natural beauty, local community involvement, conservation efforts, etc.

3. Top 10 Sustainable Mountainous Travel Destinations

3.1 The Swiss Alps, Switzerland
– Overview of the destination
– Sustainable practices: Waste management, emission reduction initiatives, etc.
– Opportunities for eco-friendly activities

3.2 The Rocky Mountains, USA
– Overview of the destination
– Sustainable practices: Wildlife protection efforts, sustainable lodging, etc.
– Opportunities for eco-friendly activities

3.3 The Himalayas, Nepal
– Overview of the destination
– Sustainable practices: Community-based tourism, efforts to reduce over-tourism, etc.
– Opportunities for eco-friendly activities

3.4 The Andes, Peru
– Overview of the destination
– Sustainable practices: Fair trade practices, eco-friendly lodging options, etc.
– Opportunities for eco-friendly activities

3.5 The Southern Alps, New Zealand
– Overview of the destination
– Sustainable practices: Carbon offsetting initiatives, protection of biodiversity, etc.
– Opportunities for eco-friendly activities

3.6 Cairngorms National Park, Scotland
– Overview of the destination
– Sustainable practices: Renewable energy initiatives, wildlife preservation, etc.
– Opportunities for eco-friendly activities

3.7 Killarney National Park, Ireland
– Overview of the destination
– Sustainable practices: Strict controls on development, protection of local flora and fauna, etc.
– Opportunities for eco-friendly activities

3.8 The Cascade Range, USA
– Overview of the destination
– Sustainable practices: Initiatives to protect endemic species, eco-accommodation, etc.
– Opportunities for eco-friendly activities

3.9 The Pyrenees, Spain/France
– Overview of the destination
– Sustainable practices: Reduction of greenhouse gas emissions, preservation of cultural heritage, etc.
– Opportunities for eco-friendly activities

3.10 Mount Kilimanjaro, Tanzania
– Overview of the destination
– Sustainable practices: Efforts to mitigate the effect of tourism on local communities, waste management initiatives, etc.
– Opportunities for eco-friendly activities

4. Weather and travel conditions for each destination
– Best times to visit
– How to reach
– Lodging Options
– Packing essentials

5. The role of travelers in promoting sustainability
– Guidelines for eco-friendly behavior
– How to choose sustainable tour operators
– The concept of carbon offsetting

6. Conclusion: The significance of promoting sustainable mountainous travel destinations to protect these natural wonders for future generations.

Each topic can be expanded upon with additional research to meet the 15000-word requirement. This outline serves to provide a detailed guidance map on how to structure the article. Various SEO keywords can be incorporated such as “sustainable mountainous travel,” “eco-friendly travel,” and “sustainable travel destinations.”